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Chapter 3 - Image Compression Manager / Image Compression Manager Reference

Image Compression Manager Functions / Working With Images

DecompressImage

The DecompressImage function allows your application to decompress a single-frame image into a pixel map structure. If you call this function when you have a picture open, the Image Compression Manager inserts the compressed image data into the picture.

pascal OSErr DecompressImage (Ptr data, 
                        ImageDescriptionHandle desc,
                        PixMapHandle dst, const Rect *srcRect, 
                        const  Rect *dstRect, short mode, 
                        RgnHandle mask);

data

Points to the compressed image data. This pointer must contain a 32-bit clean address. If you use a dereferenced, locked handle, you must call the Memory Manager's StripAddress routine before you use that handle with this parameter.

desc

Contains a handle to the image description structure that describes the compressed image.

dst

Contains a handle to the pixel map where the decompressed image is to be displayed. Set the current graphics port to the port that contains this pixel map.

srcRect

Contains a pointer to a rectangle defining the portion of the image to decompress. This rectangle must lie within the boundary rectangle of the compressed image, which is defined by (0,0) and ((**desc).width,(**desc).height). If you want to decompress the entire source image, set this parameter to nil. If the parameter is
nil, the rectangle is set to the rectangle structure of the image description structure.

dstRect

Contains a pointer to the rectangle into which the decompressed image is to be loaded. The compressor scales the source image to fit into this destination rectangle.

mode

Specifies the transfer mode for the operation. The Image Compression Manager supports the same transfer modes supported by QuickDraw's CopyBits routine.

mask

Contains a handle to a clipping region in the destination coordinate system. If specified, the compressor applies this mask to the destination image. If you do not want to mask bits in the destination, set this parameter to nil.

DESCRIPTION

The DecompressImage function presents a simplified interface to your application, eliminating some parameters for the sake of convenience.

Note that the DecompressImage function is invoked through the StdPix function (see "Working With the StdPix Function," which begins on page 3-141, for more information).

SPECIAL CONSIDERATIONS

The graphics port and the graphics device should be set to the destination before you call the DecompressImage function.

RESULT CODES

noErr	0	No error
paramErr	-50	Invalid parameter specified
memFullErr	-108	Not enough memory available
noCodecErr	-8961	The Image Compression Manager could not find the specified compressor

SEE ALSO

If you need to exert greater control over the decompression operation, use the FDecompressImage function, described in the next section.