Author: Bob Friesenhahn
Description: Documentation for ImageMagick enumerations

# Enumerations

Contents

- ClassType
- ColorspaceType
- CompositeOperator
- CompressionType
- FilterType
- GravityType
- ImageType
- InterlaceType
- LayerType
- NoiseType
- PaintMethod
- RenderingIntent
- ResolutionType

ClassType

ClassType specifies the image class.

ClassType
Enumeration | Description
UndefinedClass | Unset value.
DirectClass | Image is composed of pixels which represent literal color values.
PseudoClass | Image is composed of pixels which specify an index in a color palette.

ColorspaceType

The ColorspaceType enumeration is used to specify the colorspace that quantization (color reduction and mapping) is done under or to specify the colorspace when encoding an output image. Colorspaces are ways of describing colors to fit the requirements of a particular application (e.g. Television, offset printing, color monitors). Color reduction, by default, takes place in the RGBColorspace. Empirical evidence suggests that distances in color spaces such as YUVColorspace or YIQColorspace correspond to perceptual color differences more closely han do distances in RGB space. These color spaces may give better results when color reducing an image. Refer to quantize for more details.

When encoding an output image, the colorspaces RGBColorspace, CMYKColorspace, and GRAYColorspace may be specified. The CMYKColorspace option is only applicable when writing TIFF, JPEG, and Adobe Photoshop bitmap (PSD) files.

ColorspaceType
Enumeration | Description
UndefinedColorspace | Unset value.
RGBColorspace | Red-Green-Blue colorspace.
GRAYColorspace |
TransparentColorspace | The Transparent color space behaves uniquely in that it preserves the matte channel of the image if it exists.
OHTAColorspace |
XYZColorspace |
YCbCrColorspace |
YCCColorspace |
YIQColorspace |
YPbPrColorspace |
YUVColorspace | Y-signal, U-signal, and V-signal colorspace. YUV is most widely used to encode color for use in television transmission.
CMYKColorspace | Cyan-Magenta-Yellow-Black colorspace. CYMK is a subtractive color system used by printers and photographers for the rendering of colors with ink or emulsion, normally on a white surface.
sRGBColorspace |

CompositeOperator

CompositeOperator is used to select the image composition algorithm used to compose a composite image with an image. By default, each of the composite image pixels are replaced by the corresponding image tile pixel. Specify CompositeOperator to select a different algorithm.

CompositeOperator
Enumeration | Description
UndefinedCompositeOp | Unset value.
OverCompositeOp | The result is the union of the the two image shapes with the composite image obscuring image in the region of overlap.
InCompositeOp | The result is a simply composite image cut by the shape of image. None of the image data of image is included in the result.
OutCompositeOp | The resulting image is composite image with the shape of image cut out.
AtopCompositeOp | The result is the same shape as image image, with composite image obscuring image there the image shapes overlap. Note that this differs from OverCompositeOp because the portion of composite image outside of image's shape does not appear in the result.
XorCompositeOp | The result is the image data from both composite image and image that is outside the overlap region. The overlap region will be blank.
PlusCompositeOp | The result is just the sum of the image data. Output values are cropped to 255 (no overflow). This operation is independent of the matte channels.
MinusCompositeOp | The result of composite image - image, with overflow cropped to zero. The matte chanel is ignored (set to 255, full coverage).
AddCompositeOp | The result of composite image + image, with overflow wrapping around (mod 256).
SubtractCompositeOp | The result of composite image - image, with underflow wrapping around (mod 256). The add and subtract operators can be used to perform reverible transformations.
DifferenceCompositeOp | The result of abs(composite image - image). This is useful for comparing two very similar images.
BumpmapCompositeOp | The result image shaded by composite image.
ReplaceCompositeOp | The resulting image is image replaced with composite image. Here the matte information is ignored.
ReplaceRedCompositeOp | The resulting image is the red layer in image replaced with the red layer in composite image. The other layers are copied untouched.
ReplaceGreenCompositeOp | The resulting image is the green layer in image replaced with the green layer in composite image. The other layers are copied untouched.
ReplaceBlueCompositeOp | The resulting image is the blue layer in image replaced with the blue layer in composite image. The other layers are copied untouched.
ReplaceMatteCompositeOp | The resulting image is the matte layer in image replaced with the matte layer in composite image. The other layers are copied untouched. The image compositor requires a matte, or alpha channel in the image for some operations. This extra channel usually defines a mask which represents a sort of a cookie-cutter for the image. This is the case when matte is 255 (full coverage) for pixels inside the shape, zero outside, and between zero and 255 on the boundary. For certain operations, if image does not have a matte channel, it is initialized with 0 for any pixel matching in color to pixel location (0,0), otherwise 255 (to work properly borderWidth must be 0).

CompressionType

CompressionType is used to express the desired compression type when encoding an image. Be aware that most image types only support a sub-set of the available compression types. If the compression type specified is incompatable with the image, ImageMagick selects a compression type compatable with the image type.

CompressionType
Enumeration | Description
UndefinedCompression | Unset value.
NoCompression | No compression
BZipCompression | BZip (Burrows-Wheeler block-sorting text compression algorithm and Huffman coding) as used by bzip2 utilities
FaxCompression | CCITT Group 3 FAX compression
Group4Compression | CCITT Group 4 FAX compression (used only for TIFF)
JPEGCompression | JPEG compression
LZWCompression | Lempel-Ziv-Welch (LZW) compression (caution, patented by Unisys)
RunlengthEncodedCompression | Run-Length encoded (RLE) compression
ZipCompression | Lempel-Ziv compression (LZ77) as used in PKZIP and GNU gzip.

FilterType

FilterType is used to adjust the filter algorithm used when resizing images. Different filters experience varying degrees of success with various images and can take sigificantly different amounts of processing time. ImageMagick uses the LanczosFilter by default since this filter has been shown to provide the best results for most images in a reasonable amount of time. Other filter types (e.g. TriangleFilter) may execute much faster but may show artifacts when the image is re-sized or around diagonal lines. The only way to be sure is to test the filter with sample images.

FilterType
Enumeration | Description
UndefinedFilter | Unset value.
PointFilter | Point Filter
BoxFilter | Box Filter
TriangleFilter | Triangle Filter
HermiteFilter | Hermite Filter
HanningFilter | Hanning Filter
HammingFilter | Hamming Filter
BlackmanFilter | Blackman Filter
GaussianFilter | Gaussian Filter
QuadraticFilter | Quadratic Filter
CubicFilter | Cubic Filter
CatromFilter | Catrom Filter
MitchellFilter | Mitchell Filter
LanczosFilter | Lanczos Filter
BesselFilter | Bessel Filter
SincFilter | Sinc Filter

GravityType

GravityType specifies positioning of an object (e.g. text, image) within a bounding region (e.g. an image). Gravity provides a convenient way to locate objects irrespective of the size of the bounding region, in other words, you don't need to provide absolute coordinates in order to position an object. A common default for gravity is NorthWestGravity.

GravityType
Enumeration | Description
ForgetGravity | Don't use gravity.
NorthWestGravity | Position object at top-left of region.
NorthGravity | Postiion object at top-center of region
NorthEastGravity | Position object at top-right of region
WestGravity | Position object at left-center of region
CenterGravity | Position object at center of region
EastGravity | Position object at right-center of region
SouthWestGravity | Position object at left-bottom of region
SouthGravity | Position object at bottom-center of region
SouthEastGravity | Position object at bottom-right of region

ImageType

ImageType indicates the type classification of the image.

ImageType
Enumeration | Description
UndefinedType | Unset value.
BilevelType | Monochrome image
GrayscaleType | Grayscale image
PaletteType | Indexed color (palette) image
TrueColorType | Truecolor image
MatteType | Truecolor with opacity image
ColorSeparationType | Cyan/Yellow/Magenta/Black (CYMK) image

InterlaceType

InterlaceType specifies the ordering of the red, green, and blue pixel information in the image. Interlacing is usually used to make image information available to the user faster by taking advantage of the space vs time tradeoff. For example, interlacing allows images on the Web to be recognizable sooner and satellite images to accumulate/render with image resolution increasing over time.

Use LineInterlace or PlaneInterlace to create an interlaced GIF or progressive JPEG image.

InterlaceType
Enumeration | Description
UndefinedInterlace | Unset value.
NoInterlace | Don't interlace image (RGBRGBRGBRGBRGBRGB...)
LineInterlace | Use scanline interlacing (RRR...GGG...BBB...RRR...GGG...BBB...)
PlaneInterlace | Use plane interlacing (RRRRRR...GGGGGG...BBBBBB...)
PartitionInterlace | Similar to plane interlaing except that the different planes are saved to individual files (e.g. image.R, image.G, and image.B)

LayerType

LayerType is used as an argument when doing color separations. Use LayerType when extracting a layer from an image. MatteLayer is useful for extracting the opacity values from an image.

LayerType
Enumeration | Description
UndefinedLayer | Unset value.
RedLayer | Select red layer
GreenLayer | Select green layer
BlueLayer | Select blue layer
MatteLayer | Select matte (opacity values) layer

NoiseType

NoiseType is used as an argument to select the type of noise to be added to the image.

NoiseType
Enumeration | Description
UniformNoise | Uniform noise
GaussianNoise | Gaussian noise
MultiplicativeGaussianNoise | Multiplicative Gaussian noise
ImpulseNoise | Impulse noise
LaplacianNoise | Laplacian noise
PoissonNoise | Poisson noise

PaintMethod

PaintMethod specifies how pixel colors are to be replaced in the image. It is used to select the pixel-filling algorithm employed.

PaintMethod
Enumeration | Description
PointMethod | Replace pixel color at point.
ReplaceMethod | Replace color for all image pixels matching color at point.
FloodfillMethod | Replace color for pixels surrounding point until encountering pixel that fails to match color at point.
FillToBorderMethod | Replace color for pixels surrounding point until encountering pixels matching border color.
ResetMethod | Replace colors for all pixels in image with pen color.

RenderingIntent

Rendering intent is a concept defined by ICC Spec ICC.1:1998-09, "File Format for Color Profiles". ImageMagick uses RenderingIntent in order to support ICC Color Profiles.

From the specification: "Rendering intent specifies the style of reproduction to be used during the evaluation of this profile in a sequence of profiles. It applies specifically to that profile in the sequence and not to the entire sequence. Typically, the user or application will set the rendering intent dynamically at runtime or embedding time."

RenderingIntent
Enumeration | Description
UndefinedIntent | Unset value.
SaturationIntent | A rendering intent that specifies the saturation of the pixels in the image is preserved perhaps at the expense of accuracy in hue and lightness.
PerceptualIntent | A rendering intent that specifies the full gamut of the image is compressed or expanded to fill the gamut of the destination device. Gray balance is preserved but colorimetric accuracy might not be preserved.
AbsoluteIntent | Absolute colorimetric
RelativeIntent | Relative colorimetric

ResolutionType

By default, ImageMagick defines resolutions in pixels per inch. ResolutionType provides a means to adjust this.

ResolutionType
Enumeration | Description
UndefinedResolution | Unset value.
PixelsPerInchResolution | Density specifications are specified in units of pixels per inch (english units).
PixelsPerCentimeterResolution | Density specifications are specified in units of pixels per centimeter (metric units).