QuickTime 4 Reference

Determining the Properties of the Image File

If you want to know the dimensions of the image, call the importer's GraphicsImportGetNaturalBounds function. If you want to know other information that is represented in the image description, such as its depth or color table, call GraphicsImportGetImageDescription . If you want to extract meta-data from the image file (such as textual comments, like copyright information), call GraphicsImportGetMetaData . If you want to know information about the file format, such as the MIME types and MIME suggested file name suffixes, call GraphicsImportGetMIMETypeList .

Some image file formats can contain transparent regions, and hence may leave some pixels in their rectangular range unmodified even when drawing with a copying transfer mode and an identity matrix. If you would like to know whether a graphics importer's format supports such transparent regions, call GraphicsImportDoesDrawAllPixels . (If a graphics importer doesn't support the GraphicsImportDoesDrawAllPixels call, you can assume it will draw all pixels.)