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Images are all rectangular arrangements of pixels. The type of a pixel depends on the exact type of the image. In addition, a pixel has a color which also depends on the exact type of the image. You can think of the color as an interpretation of the pixel value by the type of image.
The coordinate system of an image has (0,0) in its upper-left corner. The x coordinate grows to the right and the y coordinate downwards.
This function returns the width and the height of the image respectively.
This function returns a two-dimensional array of pixels, whose element type depends on the exact subtype of the image.
This function returns the pixel at the coordinate indicated by the values of x and y. The type of the return value depends on the exact image type.
Set the value of the pixel at the coordinate indicated by the values of x and y. The exact type acceptable for the pixel argument depends on the exact subtype of the image. If x or y are not within the values of the width and height of the image, an error is signaled.
This function returns the color value of the pixel indicated by the values of x and y. The exact type of the return value depends on the specific subtype of the image.
Set the color value of the pixel at the coordinate indicated by the values of x and y. The exact type acceptable for the color argument depends on the exact subtype of the image. In addition, the exact color given to the pixel may be an approximation of the value of the color argument. For instance, if the image is a gray-level image, then the color given will correspond to the intensity value of the color argument. If x or y are not within the values of the width and height of the image, an error is signaled.
This class is a subclass of the image class. It is the root of a subhiearchy for manipulating images represented in various spectral formats, other than RGB. [This subhierarchy will be elaborated later in the context of the color model of Strandh and Braquelaire].
This class is a subclass of the image class. It is the root of a subhierarchy for manipulating images whose pixel colors are represented as RGB coordinates. The function image-color always returns a value of type (unsigned-byte 24) for images of this type, representing three different intensity values of 0-255.
This class is a subclass of the rgb-image class. Images of this class have pixel values of type (unsigned-byte 24). The pixel values directly represent RGB values.
This class is a subclass of the rgb-image class. Images of this class have pixel values that don't directly indicate the color of the pixel. The translation between pixel value and color may be implicit (as is the case of gray-level images) or explicit with a colormap stored in the image object.
This class is a subclass of the colormap-image class. Images of this type have pixel values that implicitely represent a gray-level. The function pixel-color always returns an RGB value that corresponds to the identical intensities for red, green, and blue, according to the pixel value.
This function returns the maximum number of levels of gray that can be represented by the image. The value returned by this function minus one would yield a color value of 255,255,255 if it were the value of a pixel.
This function returns the maximum level currently present in the image. This function may be very costly to compute, as it might have to scan the entire image.
This function returns the minimum level currently present in the image. This function may be very costly to compute, as it might have to scan the entire image.
This class is a subclass of the gray-level-image class. Images of this type have pixels represented as 8-bit unsigned pixels. The function image-pixel always returns a value of type (unsigned-byte 8) for images of this type. The function gray-image-max-levels returns 256 for all instances of this class.
This class is a subclass of the gray-level-image class. Images of this type have pixel values of type bit. The function image-pixel returns values of type bit when applied to an image of this type. The function pixel-color returns 0,0,0 for zero-valued bits and 255,255,255 for one-valued bits.