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Chapter 4 - Image Compressor Components / Image Compressor Components Reference

Functions / Indirect Functions

CDPreDecompress

Your component receives the CDPreDecompress request before decompressing an image or a band of an image. The Image Compression Manager also calls this function when processing a sequence. In that case, the Image Compression Manager calls this function whenever the parameters governing the sequence operation have changed substantially. Your component indicates whether it can perform the requested decompression operation.

pascal ComponentResult CDPreDecompress 
                                 (CodecDecompressParams *params);

params

Contains a pointer to a decompression parameters structure. The Image Compression Manager places the appropriate parameter information in that structure. See "The Decompression Parameters Structure" beginning on page 4-46 for a complete description of the decompression parameters structure.

DESCRIPTION

Your component should return a 0 result code to indicate that it can handle the request. In addition, your component indicates any limitations on its capabilities in a
compressor capability structure (see page 4-35 for a description of that structure). Return a result code of codecConditionError if your component cannot field the decompression request.

Only decompressors receive this request.

RESULT CODES

noErr	0	No error
paramErr	-50	Invalid parameter specified
codecConditionErr	-8972	Component cannot perform requested operation

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