Run Ends Image Storage Format

As of ImageGear v14.5, the Windows DIB format is no longer used for internal storage of images. So 1-bit images are now always stored internally in run ends format (also called "run lengths" format). Previous versions of ImageGear had IG_IP_convert_runs_to_DIB() and IG_IP_convert_DIB_to_runs() functions that converted the internally stored image between run ends and DIB (uncompressed packed) format. These functions are no longer necessary because conversion is performed automatically as needed.

When you read an image's pixel data using a pixel access function such as IG_DIB_raster_get(), ImageGear decompresses the pixel data for that raster and stores it in your buffer. You can specify packed (8 pixels per byte) or unpacked (1 pixel per byte) format. When you write pixel data using a pixel access function such as IG_DIB_raster_set(), ImageGear will compress and store the pixel data in run ends format. It's important to realize that this decompression and compression is the same work that was previously performed in IG_IP_convert_runs_to_DIB() and IG_IP_convert_DIB_to_runs(). However, instead of being performed on the entire image before and after processing, this work is performed on parts of the image during processing.

This section provides the following information: