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Chapter 3 - Image Compression Manager / Image Compression Manager Reference

Image Compression Manager Functions / Working With the StdPix Function

GetCompressedPixMapInfo

The GetCompressedPixMapInfo function allows your application to retrieve information about a compressed image.

pascal OSErr GetCompressedPixMapInfo (PixMapPtr pix,
                           ImageDescriptionHandle *desc, 
                           Ptr *data, long *bufferSize, 
                           DataProcRecord *dataProc, 
                           ProgressProcRecord *progressProc);

pix

Points to a structure that holds encoded compressed image data.

desc

Contains a pointer to a field that is to receive a handle to the image description structure that defines the compressed image. If you are not interested in this information, you may specify nil in this parameter.

data

Contains a pointer to a field that is to receive a pointer to the compressed image data. If the entire compressed image cannot be stored at this location, you can define a data-loading function for this operation (see the discussion of the dataProc parameter to this function). If you are not interested in this information, you may specify nil in this parameter.

bufferSize

Contains a pointer to a field that is to receive the size of the buffer to be used by the data-loading function specified by the dataProc parameter. If there is no data-loading function defined for this operation, this parameter is ignored. If you are not interested in this information, you may specify nil in this parameter.

dataProc

Contains a pointer to a data-loading function structure. If there is not enough memory to store the compressed image, the decompressor calls a function you provide that loads more compressed data (see "Data-Loading Functions" beginning on page 3-143 for more information about data-loading functions). If there is no data-loading function for this image, the function sets the dataProc field in the function structure to nil. If you are not interested in this information, you may specify nil in this parameter.

progressProc

Contains a pointer to a progress function structure. During a decompression operation, the decompressor may occasionally
call a function you provide in order to report its progress
(see "Progress Functions" beginning on page 3-146 for more information about progress functions). If there is no progress function for this image, the function sets the progressProc field in the function structure to nil. If you pass a value of -1, you obtain a standard progress function. If you are not interested in this information, you may specify nil in this parameter.

DESCRIPTION

The data in the compressed image has been encoded in a PixMap structure with the SetCompressPixMapInfo function. This is the kind of pixel map that may be passed into the StdPix function. If you pass a normal, non-encoded pixel map, GetCompressedPixMapInfo returns a paramErr result code. You use
the GetCompressedPixMapInfo function if you are intercepting calls to the StdPix function.

SPECIAL CONSIDERATIONS

The pixel map structure filled in by the GetCompressedPixMapInfo function should not be used by any other Macintosh functions. It is only to be used by the StdPix function.

RESULT CODES

paramErr

-50

Invalid parameter specified

SEE ALSO

You can set information about a compressed pixel map by calling the SetCompressedPixMapInfo function, which is described in the previous section.