Super Compressed Bitmaps

(Document and Medical Imaging toolkits)

 Super compressed bitmaps are kept compressed in memory. Only 24-bit, 8-bit, or 1-bit bitmaps can be kept super compressed. The memory requirements for super compressed bitmaps are greatly reduced compared to uncompressed bitmaps or RLE-compressed bitmaps. For more information on loading RLE compressed images, refer to Speeding up 1-bit Documents.

The data access for super compressed bitmaps is usually slower, compared to uncompressed bitmaps. The compression used for 24-bit and 8-bit bitmaps is lossy, which means multiple changes to the bitmap can produce some visual loss.

The data access is usually slower for super compressed bitmaps, but there are situations in which the data access is faster than for uncompressed bitmaps. When dealing with very large bitmaps, the O/S might swap to disk the bitmap data. In this case, the access for uncompressed bitmaps can be a lot slower than for super compressed bitmaps.

Any application that deals with large bitmaps of tens or hundreds of MB should consider using super compressed bitmaps.

To allocate storage for a super compressed bitmap, call L_AllocateBitmap. To initialize and allocate a supercompressed bitmap, call L_CreateBitmap.

The L_LoadFile function can be used to load 1-bit, 8-bit or 24-bit images as super compressed.

The L_ChangeBitmapCompression function can be used to super compress 1-bit, 8-bit, or 24-bit bitmaps, as well as, uncompress bitmaps and compress 1-bit bitmaps using RLE compression.

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