RMagick 1.15.0: class Image (instance methods, part 3)

Description

Creates an image that contains 9 small versions of the receiver image. The center image is the unchanged receiver. The other 8 images are variations created by transforming the receiver according to the specified preview type with varying parameters.

A preview image is an easy way to "try out" a transformation method.

Arguments

One of the following PreviewType constants:

RotatePreview
ShearPreview
RollPreview
HuePreview
SaturationPreview
BrightnessPreview
GammaPreview
SpiffPreview
DullPreview
GrayscalePreview
QuantizePreview
DespecklePreview
ReduceNoisePreview
AddNoisePreview
SharpenPreview

BlurPreview
ThresholdPreview
EdgeDetectPreview
SpreadPreview
SolarizePreview
ShadePreview
RaisePreview
SegmentPreview
SwirlPreview
ImplodePreview
WavePreview
OilPaintPreview
CharcoalDrawingPreview
JPEGPreview

Returns

A new image

Example

This half-size preview demonstrates the SolarizePreview argument.

Magick API

PreviewImage

Description

Adds or removes a ICM, IPTC, or generic profile from an image. If profile is nil, the specified profile is removed from the image. Use profile('*', nil) to remove all profiles from the image.

Arguments

name: The profile name, or "*" to represent all the profiles in the image.
profile: The profile value, or nil to cause the profile to be removed.

Returns

self

Magick API

ProfileImage

Notes

×Magick does not automatically remove profiles when resizing images. If you are trying to make your JPEG thumbnail images as small as possible, use profile! to remove any profiles from the image as well. Also see strip!

Description

If called with an associated block, properties runs the block once for each property defined for the image. The block arguments are the property name and its value. If there is no block, properties returns a hash with one element for each property. The hash key is the property name and the associated value is the property value.

Returns

If called without a block, returns a hash, otherwise returns self.

Note

The EXIF property is not created until the first time an EXIF tag or entry number is referenced.

Description

Analyzes the colors within a reference image and chooses a fixed number of colors to represent the image. The goal of the algorithm is to minimize the difference between the input and output image while minimizing the processing time.

Arguments

number_colors: The maximum number of colors in the result image. Must be <= MaxRGB.
colorspace: The colorspace to quantize in. Color reduction, by default, takes place in the RGB color space. Empirical evidence suggests that distances in color spaces such as YUV or YIQ correspond to perceptual color differences more closely than do distances in RGB space. The Transparent color space behaves uniquely in that it preserves the matte channel of the image if it exists.
dither: Set to true to apply Floyd/Steinberg error diffusion to the image. When the size of the color palette is less than the image colors, this trades off spacial resolution for color resolution by dithering to achieve a similar looking image.
tree_depth: The tree depth to use while quantizing. The values 0 and 1 support automatic tree depth determination. The tree depth may be forced via values ranging from 2 to 8. The ideal tree depth depends on the characteristics of the input image, and may be determined through experimentation.
measure_error: Set to true to calculate quantization errors when quantizing the image.

Returns

A new image

Example

See the example for colorize.

Magick API

QuantizeImage

Description

Performs the requested integer arithmetic operation on the selected channel of the image. This method allows simple arithmetic operations on the component values of all pixels in an image. Of course, you could also do this in Ruby using get_pixels and store_pixels, or view, but quantum_operator will be faster, especially for large numbers of pixels, since it does not need to convert the pixels from C to Ruby.

Arguments

operator

One of the following QuantumExpressionOperator constants:

AddQuantumOperator
AndQuantumOperator
DivideQuantumOperator
LShiftQuantumOperator
MaxQuantumOperator^*
MinQuantumOperator^*
MultiplyQuantumOperator
OrQuantumOperator
RShiftQuantumOperator
SubtractQuantumOperator
XorQuantumOperator

^* Available in ImageMagick 6.2.0 and later.

rvalue

a Numeric operation rvalue.

channel

A ChannelType value. The default is to operate on all channels.

Returns

self

Example

Divide the red component of all the pixels in the image by 2:

img.quantum_operator(DivideQuantumOperator, 2, RedChannel)

Magick API

QuantumOperatorRegionImage (GraphicsMagick 1.1), EvaluateImageChannel (ImageMagick)

Description

Applies a radial blur to the image.

Arguments

angle: Amount of blur, in degrees

Returns

A new image

Example

Magick API

RadialBlurImage

Description

Applies a radial blur to the selected image channels.

Arguments

angle: Amount of blur, in degrees
channel...: 0 or more ChannelType arguments. If no channels are specified, all the channels are blurred.

Returns

A new image

Magick API

RadialBlurImageChannel (available in ImageMagick 6.2.4)

Description

Creates a simulated three-dimensional button-like effect by lightening and darkening the edges of the image.

Arguments

width: The width of the raised edge in pixels. The default is 6.
height: The height of the raised edge in pixels. The default is 6.
raised: If true, the image is raised, otherwise lowered.

Returns

A new image

Example

Magick API

RaiseImage

Description

Changes the value of individual pixels based on the intensity of each pixel compared to a random threshold. The result is a low-contrast, two color image.

Arguments

thresholds: A geometry string containing LOWxHIGH thresholds. The string is in the form `XxY'. The Y value may be omitted, in which case it is assigned the value MaxRGB-X. If an % appears in the string then the values are assumed to be percentages of MaxRGB. If the string contains 2x2, 3x3, or 4x4, then an ordered dither of order 2, 3, or 4 will be performed instead. A Geometry object may be used as well.
channel...: 0 or more ChannelType arguments. If no channels are specified, all the channels are thresholded.

Returns

A new image

Example

geom = Geometry.new(MaxRGB/2)
random_threshold_channel(geom, RedChannel)

Magick API

RandomThresholdImageChannel

Description

Use this method to translate, scale, shear, or rotate image colors. Although you can use variable sized matrices, typically you use a 5×5 for an RGBA image and a 6×6 for CMYKA. Populate the last row with normalized values to translate.

Arguments

An array of Float values representing the recolor matrix.

Magick API

RecolorImage (introduced in ImageMagick 6.3.1)

Description

Smooths the contours of an image while still preserving edge information. The algorithm works by replacing each pixel with its neighbor closest in value.

Arguments

radius: A neighbor is defined by radius. Use a radius of 0 and reduce_noise selects a suitable radius for you.

Returns

A new image

Example

The left side of the image has been modified by add_noise. The right side has been filtered by reduce_noise(0).

Magick API

ReduceNoiseImage

Description

Resample image to specified horizontal and vertical resolution.

Resize the image so that its rendered size remains the same as the original at the specified target resolution. For example, if a 300 DPI image renders at 3 inches by 2 inches on a 300 DPI device, when the image has been resampled to 72 DPI, it will render at 3 inches by 2 inches on a 72 DPI device. Note that only a small number of image formats (e.g. JPEG, PNG, and TIFF) are capable of storing the image resolution. For formats which do not support an image resolution, the original resolution of the image must be specified via the density attribute prior to specifying the resample resolution.

Arguments

horizontal_res: the target horizontal resolution. The default is 72.0.
vertical_res: the target vertical resolution. The default is horizontal_res.

Description

Changes the size of the receiver to the specified dimensions.

Arguments

You can specify the new size in two ways. Either specify the new width and height explicitly, or specify a scale factor, a number that represents the percentage change.

Use the change_geometry method to resize an image with constraints such as "maintain the current proportions."

new_width, new_height: The desired width and height.
filter: The filter to use when resizing. If you do not specify a filter argument, resize uses the value of the receiver's filter attribute. Most of the filters are FIR (finite impulse response), however, Bessel, Gaussian, and Sinc are IIR (infinite impulse response). Bessel and Sinc are windowed (brought down to zero) with the Blackman filter.
support: Values > 1 increase the blurriness. Values < 1 increase the sharpness. If this argument is not specified, resize uses the value of the receiver's blur attribute.
scale_factor: You can use this argument instead of specifying the desired width and height. The percentage size change. For example, 1.25 makes the new image 125% of the size of the receiver. The scale factor 0.5 makes the new image 50% of the size of the receiver.

Returns

A new image

Magick API

ResizeImage

Description

In-place form of resize.

Returns

self

Description

A convenience method. Resize the image to fit within the specified dimensions while retaining the original aspect ratio.

Arguments

new_width, new_height: The maximum width and height of the resized image. In order to retain the aspect ratio of the input image, the actual dimensions of the resized image may be different but will not be larger than the specified values.

Returns

A new image

Description

In-place form of resize_to_fit.

Returns

self

Description

Offsets an image as defined by x_offset and y_offset.

Arguments

x_offset: The number of columns to offset the image.
y_offset: The number of rows to offset the image.

Returns

A new image

Example

This image has been offset 25% in both directions.

Magick API

RollImage

Description

Rotate the receiver by the specified angle. Positive angles rotate clockwise while negative angles rotate counter-clockwise. New pixels introduced by the rotation are the same color as the current background color. Set the background color to "none" to make the new pixels transparent black.

Arguments

amount: The number of degrees to rotate the image.
qualifier: If present, either ">" or "<". If ">", rotates the image only if the image's width exceeds its height. If "<" rotates the image only if its height exceeds its width. If this argument is omitted the image is always rotated.

Returns

A new image, or nil if the image was not rotated because it did not meet the qualification specified by the second argument.

Example

Magick API

RotateImage

Description

In-place form of rotate.

Returns

self, or nil if the image was not rotated because it did not meet the qualification specified by the second argument.

Description

Scales an image to the desired dimensions with pixel sampling. Unlike other scaling methods, this method does not introduce any additional color into the scaled image.

Arguments

new_width, new_height: The desired width and height.
scale_factor: You can use this argument instead of specifying the desired width and height. The percentage size change. For example, 1.25 makes the new image 125% of the size of the receiver. The scale factor 0.5 makes the new image 50% of the size of the receiver.

Returns

A new image

Magick API

SampleImage

Description

In-place form of sample.

Returns

self

Description

Changes the size of an image to the given dimensions.

Arguments

new_width, new_height: The desired width and height.
scale_factor: You can use this argument instead of specifying the desired width and height. The percentage size change. For example, 1.25 makes the new image 125% of the size of the receiver. The scale factor 0.5 makes the new image 50% of the size of the receiver.

Returns

A new image

Magick API

ScaleImage

Description

In-place form of scale.

Returns

self

Description

Segments an image by analyzing the histograms of the color components and identifying units that are homogeneous with the fuzzy c-means technique.

Arguments

colorspace: A ColorspaceType value. Empirical evidence suggests that distances in YUV or YIQ correspond to perceptual color differences more closely than do distances in RGB space. The image is then returned to RGB colorspace after color reduction.
cluster_threshold: The number of pixels in each cluster must exceed the the cluster threshold to be considered valid.
smoothing_threshold: The smoothing threshold eliminates noise in the second derivative of the histogram. As the value is increased, you can expect a smoother second derivative.
verbose: If true, segment prints detailed information about the identified classes.

Returns

A new image

Example

segment(Magick::YUVColorspace, 0.4, 0.4)

Magick API

SegmentImage

Description

Applies a special effect to the image, similar to the effect achieved in a photo darkroom by sepia toning.

Arguments

threshold: Threshold ranges from 0 to MaxRGB and is a measure of the extent of the sepia toning. A threshold of 80% is a good starting point for a reasonable tone. The default is MaxRGB.

Returns

self

Example

Magick API

SepiaToneImage (available in ImageMagick 6.2.1)

Description

Sets the depth of the image channel.

Arguments

channel: A ChannelType value
depth: The desired depth (must be no greater than QuantumDepth)

Returns

self

Magick API

SetImageChannelDepth

Description

Shines a distant light on an image to create a three-dimensional effect. You control the positioning of the light with azimuth and elevation; azimuth is measured in degrees off the x axis and elevation is measured in pixels above the Z axis.

Arguments

shading: If true, shade shades the intensity of each pixel.
azimuth, elevation: The light source direction. The azimuth is measured in degrees. 0° is at 9 o'clock. Increasing values move the light source counter-clockwise.

Returns

A new image

Example

shade(true, 50, 50)

Magick API

ShadeImage

Description

Draws the shadow of opaque parts of the image. This method only works when the image has opaque parts and transparent parts. Note that the resulting image is just the shadow. You must composite the original image over the shadow to produce the shadowed results.

Arguments

x_offset: The shadow x-offset
y_offset: The shadow y-offset
sigma: The standard deviation of the Gaussian operator used to produce the shadow. The higher the number, the "blurrier" the shadow, but the longer it takes to produce the shadow. Must be > 0.0.
opacity: The percent opacity of the shadow. May be either a number between 0.1 and 1.0, or a string in the form "NN%" between "1%" and "100%". If the percentage is greater than 100 it is reduced to 100.

Returns

A new image

Example

Magick API

ShadowImage (available in ImageMagick 6.1.7)

Notes

The shadow image is 2×sigma pixels larger on a side than the original image, as can be seen in the example above.

Description

Sharpens an image. We convolve the image with a Gaussian operator of the given radius and standard deviation (sigma). For reasonable results, radius should be larger than sigma. Use a radius of 0 and sharpen selects a suitable radius for you.

Arguments

The radius and standard deviation of the Gaussian operator.

Returns

A new image

Magick API

SharpenImage

Description

Sharpens one or more image channels. We convolve the image with a Gaussian operator of the given radius and standard deviation (sigma) . For reasonable results, radius should be larger than sigma. Use a radius of 0 and sharpen_channel selects a suitable radius for you.

Arguments

radius, sigma: The radius and standard deviation of the Gaussian operator.
channel...: 0 or more ChannelType arguments. If no channels are specified, all the channels are sharpened.

Returns

A new image

Magick API

SharpenImageChannel (available in ImageMagick 6.0.1)

Description

Removes pixels from the edges of the image, leaving the center rectangle.

Arguments

width: The number of pixels to remove from each side of the receiver, not to exceed half the original width.
height: The number of pixels to remove from the top and bottom of the receiver, not to exceed half the original height.

Returns

A new image

Example

Magick API

ShaveImage

Description

In-place form of shave.

Returns

self

Description

Shearing slides one edge of an image along the X or Y axis, creating a parallelogram. An X direction shear slides an edge along the X axis, while a Y direction shear slides an edge along the Y axis. The amount of the shear is controlled by a shear angle. For X direction shears, x_shear is measured relative to the Y axis, and similarly, for Y direction shears y_shear is measured relative to the X axis. Empty triangles left over from shearing the image are filled with the background color.

Arguments

The X and Y shear angles, measured in degrees. These values must not be 180.0. If either value is 0, no shearing will occur.

Returns

A new image

Example

Magick API

ShearImage

Description

Adjusts the contrast of an image channel with a non-linear sigmoidal contrast algorithm. Increases the contrast of the image using a sigmoidal transfer function without saturating highlights or shadows.

Arguments

contrast: indicates how much to increase the contrast (0 is none; 3 is typical; 20 is pushing it)
midpoint: indicates where midtones fall in the resultant image (0 is white; 50% is middle-gray; 100% is black)
sharpen: Set sharpen to true to increase the image contrast otherwise the contrast is reduced.
channel...: 0 or more ChannelType arguments. If no channels are specified, all the channels are adjusted.

Returns

A new image

Magick API

SigmoidalContrastImageChannel (available in ImageMagick 6.2.1)

Description

Computes a message digest from an image pixel stream with an implementation of the NIST SHA-256 Message Digest algorithm. This signature uniquely identifies the image and is convenient for determining if an image has been modified or whether two images are identical.

×Magick adds the computed signature to the image's properties.

Returns

The signature as a 64-character string.

Example

img = Image.read('ex/images/Flower_Hat.jpg').first »
  ex/images/Flower_Hat.jpg JPEG 200x250 DirectClass 8-bit 9761b
img.properties »
  {"comment"=>"File written by Adobe Photoshop\250 4.0"}
img.signature »
  "485e01ecba1a1f47924d67b887cb07b474f695841733796dfa3c2876965c7e8b"
img.properties »
  {"signature"=>"485e01ecba1a1f47924d67b887cb07b474f695841733796dfa3c2876965c7e8b",
   "comment"=>"File written by Adobe Photoshop\250 4.0"}

Magick API

SignatureImage

Description

Simulates a pencil sketch. For best results start with a grayscale image.

Arguments

radius, sigma: The radius and sigma of the Gaussian operator
angle: The angle toward which the image is sketched.

Returns

A new image

Example

Magick API

SketchImage (available in ImageMagick 6.2.8)

Description

Applies a special effect to the image similar to the effect achieved in a photo darkroom by selectively exposing areas of photo sensitive paper to light.

Arguments

Ranges from 0 to MaxRGB and is a measure of the extent of the solarization. The default is 50.

Returns

A new image

Example

Magick API

SolarizeImage

Description

Splice a solid color into the image as defined by the x, y, width, and height arguments. This method is the opposite of chop.

Arguments

x, y, width, height: Describe the rectangle to be spliced.
color: The color to be spliced. Either a color name or a pixel. If omitted, uses the image's background color.

Returns

A new image

Example

Magick API

SpliceImage

Description

Randomly displaces each pixel in a block defined by the radius parameter.

Returns

A new image

Example

Magick API

SpreadImage

Description

Computes the minimum, maximum, mean, standard deviation, and variance for each channel in the image.

Returns

The statistics method returns a Statistics class object. This class defines four channel attributes: red, green, blue, and opacity. Each channel attribute is a Statistics::Channel class object. This class defines 5 statistic attributes: min, max, mean stddev, and var. See the example below.

Example

require 'pp'

img = Image.read("Flower_Hat.jpg").first
stats = img.statistics

pp stats »
    #<Magick::Statistics
    red=
      #<Magick::Statistics::Channel
      max=1.0,
      min=0.0,
      mean=0.627182352941187,
      stddev=0.231399683489667,
      var=0.0535458135191179>,
    green=
      #<Magick::Statistics::Channel
      max=1.0,
      min=0.0,
      mean=0.571999607843132,
      stddev=0.22246563644744,
      var=0.0494909593999647>,
    blue=
      #<Magick::Statistics::Channel
      max=1.0,
      min=0.0,
      mean=0.508869725490209,
      stddev=0.269422111063184,
      var=0.0725882739297426>,
    opacity=
      #<Magick::Statistics::Channel
      max=0.0,
      min=0.0,
      mean=0.0,
      stddev=0.0,
      var=0.0>>

p stats.red.stddev » 0.231399683489667

Magick API

GetImageStatistics (available in GraphicsMagick 1.1)

Description

Hides a digital watermark in the receiver. You can retrieve the watermark by reading the file with the stegano: prefix, thereby proving the authenticity of the file.

The watermarked image must be saved in a lossless RGB format such as MIFF, or PNG. You cannot save a watermarked image in a lossy format such as JPEG or a pseudocolor format such as GIF. Once written, the file must not be modified or processed in any way.

Arguments

watermark: An image or imagelist to be used as the watermark. The watermark must be grayscale and should be substantially smaller than the receiver. The recovery time is proportional to the size of the watermark.
offset: The starting position within the receiver at which the watermark will be hidden. When you retrieve the watermark from the file, you must supply this value, along with the width and height of the watermark, in the size optional parameter to the read method.

Returns

A copy of the image containing the embedded watermark.

Example

Magick API

SteganoImage

Description

Combines two images and produces a single image that is the composite of a left and right image of a stereo pair. Special red-green stereo glasses are required to view this effect.

Arguments

Another image or imagelist. If the argument is an imagelist, uses the current image.

Returns

A new image

Magick API

StereoImage

Description

Replace the pixels in the specified rectangle with the pixels in the pixels array.

Arguments

x, y: The x- and y-offset of the rectangle to be replaced.
columns, rows: The number of rows and columns in the rectangle.
pixels: An array of pixels. The number of pixels in the array must be the same as the number of pixels in the rectangle, that is, rows*columns.

Returns

The image, with the rectangle suitably altered.

Example

Also see the example for get_pixels.

Magick API

SetImagePixels, SyncImagePixels

Description

Strips an image of all profiles and comments.

Returns

self

Magick API

StripImage (available in ImageMagick and GraphicsMagick 1.1)

Description

Swirls the pixels about the center of the image, where degrees indicates the sweep of the arc through which each pixel is moved. You get a more dramatic effect as the degrees move from 1 to 360.

Arguments

The number of degrees to swirl the image.

Returns

A new image

Example

This example is an animated image. Mouse over the image to start the animation.

Magick API

SwirlImage

Description

Replaces the target pixel at x, y and its neighbors that are not the border color with copies of the texture image. Use the fuzz attribute to specify how closely a pixel must match the border color.

Arguments

x, y: The x- and y-offset of the target pixel.
texture: An image or imagelist. If an imagelist, uses the current image.

Returns

A new image

Example

In this example the target is the pixel in the center of the image. The texture - in this case a picture of a girl in a flowered hat - replaces this pixel and its neighbors until reaching a black pixel. Mouse over the image to see the original image. Notice the plum-colored circles are replaced as well. Compare this result with the result of texture_floodfill, below.

Magick API

ColorFloodfillImage

Description

Replaces the target pixel at x, y and its neighbors that are the same color with the texture image. By default, the neighbor pixels must be exactly the same color as the target pixel. Use the fuzz attribute to specify how much difference is acceptable.

Arguments

x, y: The x- and y-offset of the target pixel.
texture: An image or imagelist. If an imagelist, uses the current image.

Returns

A new image

Example

In this example the target is the pixel in the center of the image. The texture - in this case a picture of a girl in a flowered hat - replaces this pixel and its same-colored neighbors. Mouse over the image to see the original image. Notice the plum-colored circles are not replaced. Compare this result with the result of texture_fill_to_border, above.

Magick API

ColorFloodfillImage

Description

Changes the value of individual pixels based on the intensity of each pixel compared to threshold. The result is a high-contrast, two color image.

Arguments

A value between 0 and MaxRGB.

Returns

A new image

Example

threshold(Magick::MaxRGB*0.55)

Magick API

ThresholdImage

Description

The thumbnail method is a fast resizing method suitable for use when the size of the resulting image is < 10% of the original.

Arguments

You can call thumbnail with either the new width and height or the scale factor.

new_width, new_height: The desired width and height in pixels.
scale_factor: The desired size represented as a floating-point number. For example, to make a thumbnail that is 9.5% of the size of the original image, use 0.095.

Returns

A new image

Example

img = Magick::Image.read("images/Cheetah.jpg").first
thumbnail = img.thumbnail(img.columns*0.09, img.rows*0.09)

Magick API

ThumbnailImage

Description

In-place form of thumbnail.

Returns

self

Description

Creates a Binary Large OBject, a direct-to-memory version of the image. The from_blob method constructs an image from a BLOB created by this method.

Arguments

No required arguments, however you can specify the image format (such as JPEG, PNG, etc.) and depth by calling the format and depth attributes, as well as other Image::Info attributes as appropriate, in a block associated with the method.

Returns

A string containing the image data represented as a BLOB.

Example

Magick API

ImageToBlob

Description

Returns the color name for a pixel. Unlike the Pixel#to_color method, to_color uses the depth and matte attributes of the image to determine the color name.

Arguments

A Pixel object.

Returns

A color name.

Example

img = Image.read('ex/images/Flower_Hat.jpg').first
» ex/images/Flower_Hat.jpg JPEG 200x250 DirectClass 8-bit 9761b
pixel = img.pixel_color(img.columns/2, img.rows/2)
» #<struct Magick::Pixel red=216, green=147, blue=106, opacity=0>
img.to_color(pixel)
» "#D8936A"

Magick API

QueryColorname

Description

Changes the opacity value of all the pixels that match color to the value specified by opacity. By default the pixel must match exactly, but you can specify a tolerence level by setting the fuzz attribute on the image.

Arguments

color: Either a color name or a pixel.
opacity: The new opacity value, either an opacity value or a number between 0 and MaxRGB. The default is TransparentOpacity.

Returns

A new image

Example

Mouse over the image to see the original. In this example, all the black pixels are made transparent. The resulting image has been composited over a plasma background, which shows through the transparent pixels.

Magick API

TransparentImage

Description

Creates a horizontal mirror image by reflecting the pixels around the central y-axis while rotating them by 90 degrees.

Returns

A new image

Example

Magick API

TransposeImage (available in ImageMagick 6.2.8)

Description

In-place form of transpose.

Returns

self

Description

Creates a vertical mirror image by reflecting the pixels around the central x-axis while rotating them by 270 degrees

Returns

A new image

Example

Magick API

TransposeImage (available in ImageMagick 6.2.8)

Description

In-place form of transverse.

Returns

self

Description

Removes the edges that are exactly the same color as the corner pixels. Use the fuzz attribute to make trim remove edges that are nearly the same color as the corner pixels.

Returns

A new image

Example

Magick API

CropImage

In-place form of trim.

Returns

self

Description

Constructs a new image with one pixel for each unique color in the image. The new image has 1 row. The row has 1 column for each unique pixel in the image.

Returns

A new image

Magick API

UniqueImageColors (available in ImageMagick 6.2.9)

Description

Sharpens an image. We convolve the image with a Gaussian operator of the given radius and standard deviation (sigma). For reasonable results, radius should be larger than sigma. Use a radius of 0 and unsharp_mask selects a suitable radius for you.

Arguments

All arguments are optional.

radius: The radius of the Gaussian operator. The default is 0.0.
sigma: The standard deviation of the Gaussian operator. A good starting value is 1.0, which is the default.
amount: The percentage of the blurred image to be added to the receiver, specified as a fraction between 0 and 1.0. A good starting value is 1.0, which is the default.
threshold: The threshold needed to apply the amount, specified as a fraction between 0 and 1.0. A good starting value is 0.05, which is the default.

Returns

A new image

Example

Magick API

UnsharpMaskImage

Description

Sharpens an image. We convolve the image with a Gaussian operator of the given radius and standard deviation (sigma). For reasonable results, radius should be larger than sigma. Use a radius of 0 and unsharp_mask_channel selects a suitable radius for you.

Only the specified channels are sharpened.

Arguments

All arguments are optional.

radius: The radius of the Gaussian operator. The default is 0.0.
sigma: The standard deviation of the Gaussian operator. A good starting value is 1.0, which is the default.
amount: The percentage of the blurred image to be added to the receiver, specified as a fraction between 0 and 1.0. A good starting value is 1.0, which is the default.
threshold: The threshold needed to apply the amount, specified as a fraction between 0 and 1.0. A good starting value is 0.05, which is the default.
channel...: 0 or more ChannelType arguments. If no channels are specified, all the channels are sharpened. This is the equivalent of unsharp_mask.

Returns

A new image

Magick API

UnsharpMaskImageChannel (available in ImageMagick 6.1.0)

Description

View is a convenience method that supports getting and setting individual image pixels by [i][j] coordinates. With no associated block, view returns an Image::View object. If the optional code block is given, it will be passed the Image::View object as an argument. The sync method will be called automatically when the block terminates. In this case, view returns nil.

Arguments

x, y: The offset of the view from the top-left corner of the image. Within the view, pixels are relative to the top-left corner of the view, not the image.
width, height: The width and height of the view. The view may not extend past the boundaries of image.

Returns

If the optional code block is present, view returns nil. If it is not present, view returns an Image::View object.

See

Image::View

Examples

The example image below has been scaled 500% for clarity.

img = Image.new(40, 40) {self.background_color = 'lightcyan2'}

# The view is 400 pixels square, starting at
# column 10, row 5 from the top of the image.
img.view( 10, 5, 20, 20) do |view|

    # Set all the pixels in the view to green.
    view[][] = Pixel.new(0, MaxRGB)

    # Change the top and bottom rows to red.
    view[0][] = 'red'
    view[-1,1][] = 'red'

    # Set 6 pixels to black.
    view[[13,15]][[12,14,16]] = 'black'

    # Set 1 pixel to yellow.
    view[5][7] = 'yellow'

    # Change the green channel of all the
    # pixels on row 8.
    view[8][].green = MaxRGB/2

    # Change the blue channel of 8 pixels
    # on column 10.
    view[4,8][10].blue = MaxRGB
end

Notes

The view method introduces a relatively high level of overhead to pixel manipulation compared to methods that use the ×Magick API to identify and change pixels. I recommend that you use view only when the number of pixels identified in the view is fairly small (a few thousand to a few hundred thousand, depending on your patience and the speed of your computer) and you need this degree of control.

Description

Gradually shades the edges of the image by transforming the pixels into the background color.

Arguments

x: Influences the amount of background color in the horizontal dimension. Larger values of x make the vignette narrower. This argument should be positive and less than image.columns / 2. This argument is optional. If omitted, the default value is 0.10 * image.columns.
y: Influences the amount of background color in the vertical dimension. Larger values of y make the vignette shorter. This argument should be positive and less than image.rows / 2. This argument is optional. If omitted, the default value is 0.10 * image.rows.
radius, sigma: Controls the amount of blurring. Larger values of sigma increase the blurring at the expense of increased execution time. In general, radius should be larger than sigma, although if radius is 0 then ×Magick will choose a suitable value. Sigma must be non-zero. Choose a very small value for sigma to produce a "hard" edge.

Returns

A new image

Example

Magick API

VignetteImage (available in ImageMagick 6.2.6)

Notes

The image produced by vignette is very similar to the image produced by RMagick's vignette.rb example script. However, the example script gives you more control over the size, shape, and background color of the vignette.

Description

Composites a watermark image on the target image using the Modulate composite operator. This composite operation operates in the HSL colorspace and combines part of the lightness, part of the saturation, and all of the hue of each pixel in the watermark with the corresponding pixel in the target image

Arguments

mark: The watermark image. Either an imagelist or an image. If an imagelist, uses the current image.
lightness: The fraction of the lightness component of the watermark pixels to be composited onto the target image. Must be a non-negative number or a string in the form "NN%". If lightness is a number it is interpreted as a percentage. Both 0.25 and "25%" mean 25%. The default is 100%.
saturation: The fraction of the saturation component of the watermark pixels to be composited onto the target image. Must be a non-negative number or a string in the form "NN%". If lightness is a number it is interpreted as a percentage. Both 0.25 and "25%" mean 25%. The default is 100%.
x_offset: The offset of the watermark, measured from the left-hand side of the target image. The default is 0.
y_offset: The offset of the watermark, measured from the top of the target image. The default is 0.

Watermark can be called with a gravity argument or without. When a gravity argument is specified but the x- and y-offsets are omitted, the watermark is positioned based on the value of the gravity argument:

NorthWestGravity: The watermark abuts the top and left sides of the image.
NorthGravity: The watermark is centered left-to-right and abuts the top of the image.
NorthEastGravity: The watermark abuts the top and right sides of the image.
EastGravity: The watermark is centered top-to-bottom and abuts the right side of the image.
SouthEastGravity: The watermark abuts the bottom and right sides of the image.
SouthGravity: The watermark is centered left-to-right and abuts the bottom of the image.
SouthWestGravity: The watermark abuts the bottom and left sides of the image.
WestGravity: The watermark is centered top-to-bottom and abuts the left side of the image.
CenterGravity: The watermark is centered left-to-right and top-to-bottom.

When the gravity argument is present and the x-offset (and optionally the y-offset) is present, the x- and y-offset are measured from the right and/or bottom edges of the target image based on the value of gravity. If the argument is NorthEastGravity, EastGravity, or SouthEastGravity, the x-offset is measured from the right side of the image. If the argument is SouthEastGravity, SouthGravity, or SouthWestGravity, the y-offset is measured from the bottom of the image. All other values are ignored and the x- and y-offset are measured from the upper-left corner of the image.

Returns

A new image

Example

See "Watermarking with Images" in Anthony Thyssen's Examples of ImageMagick Usage.

Description

Creates a "ripple" effect in the image by shifting the pixels vertically along a sine wave whose amplitude and wavelength is specified by the given parameters.

Returns

A new image

Example

Magick API

WaveImage

Description

Creates a "wet floor" reflection. The reflection is an inverted copy of the image that changes from partially transparent to entirely transparent. By default only the bottom third of the image appears in the reflection.

Note that the output image is just the reflection. This makes it easy to apply further transformations to the reflection before combining it with the original image.

Arguments

initial: A value between 0.0 and 1.0 that specifies the initial percentage of transparency. Higher values cause the top of the reflection to be more transparent, lower values less transparent. The default is 0.5, which means that the top of the reflection is 50% transparent.
rate: A non-negative value that specifies how rapidly the reflection transitions from the initial level of transparency to entirely transparent. The default value is 1.0, which means that the transition occurs in 1/3 the image height. Values greater than 1.0 speed up the transition (the reflection will have fewer rows), values lower than 1.0 slow down the transition (the reflection will have more rows). A value of 0.0 means that the level of transparency will not change.

Returns

A new image

Example

Here are four examples of wet_floor. The top image shows the result of appending the default reflection to the original image. The second image shows the result of decreasing the initial transparency to 0.25 and using 0.5 as the rate argument. The third image uses the same reflection as the second image but has a slant added. The bottom image is the same as the third image but with a ripple effect.

Description

Forces all pixels above the threshold into white while leaving all pixels below the threshold unchanged.

Arguments

Each channel argument is a number between 0 and MaxRGB. All arguments except the first may be omitted. If the green_channel or blue_channel argument is omitted, the default value is the red_channel value. If the opacity_channel argument is omitted, the default value is OpaqueOpacity.

Returns

A new image

Magick API

WhiteThresholdImage

Description

Writes the image to the specified file. ×Magick determines image format from the prefix or extension.

If the argument is an open file, ×Magick will write the image in its current format. You can force a different format by setting the image's format attribute.

Arguments

A file name or open file object. You may also specify optional arguments by setting Image::Info attributes in an associated block.

Returns

self, or nil if the image format cannot be determined.

Example

Almost all of the examples call write.

Magick API

WriteImage

RMagick 1.15.0 User's Guide and Reference

class Image < Object (class and instance methods, part 3) mixes in Comparable

Table of Contents

instance methods

instance methods

preview

Description

Arguments

Returns

Example

Magick API

profile!

Description

Arguments

Returns

See also

Magick API

Notes

properties

Description

Returns

See also

Note

quantize

Description

Arguments

Returns

Example

See also

Magick API

quantum_operator

Description

Arguments

Returns

Example

See also

Magick API

radial_blur

Description

Arguments

Returns

Example

See also

Magick API

radial_blur_channel

Description

Arguments

Returns

See also

Magick API

raise

Description

Arguments

Returns

Example

Magick API

random_threshold_channel

Description

Arguments

Returns

Example

See also

Magick API

recolor

Description

Arguments

Magick API

reduce_noise

Description

Arguments

Returns

Example

See also

Magick API

resample

Description

Arguments

resize

Description

Arguments

class Image < Object (class and instance methods, part 3)
mixes in Comparable