BMP Suite

This is a small suite of test images in the BMP image file format. It currently consists of 28 images with various bit depths, compression types, etc.

Download:

• The BMP Suite images.
• The source code used to generate most of the images. (In C; for Windows only. Does not generate the compressed images.)

View the reference page to confirm what the images are supposed to look like. This is also included in the BMP Suite download.

Please email me if you have questions or comments.

The rest of this page contains additional random information that you probably don't care about.

Warning

There does not seem to be any official, well-defined, specification for the BMP image file format. Therefore I cannot, even in principle, guarantee that these test files are actually valid BMP files. The main guidelines I used for deciding what is legal in a BMP is whether the Windows graphics API and the Windows "Paint" program can handle the file, and that they seem to be correct according to Microsoft's definitions of various data structures such as BITMAPINFOHEADER.

This suite contains "Version 3" (and one older) bitmaps. Microsoft has also invented "Version 4" and "Version 5" bitmaps. It may be technically legal to place newer version bitmaps into a BMP file, but this is rarely done.

There are too many different combinations of fields in a BMP file to create a test file for each combination, so I basically chose one typical image and then created a bunch of variations of it. This "typical" image is g08.bmp, which has the following properties:

• Size of 127 pixels wide, 64 pixels high. 127 is more likely to reveal problems than 128, because scan lines are padded to a 4-byte boundary.
• No compression
• 8 bits-per-pixel (bpp)
• 256-color palette
• biClrUsed field set to 0 (which means "palette has 2^bpp colors")
• biClrImportant field set to 0 (which means "all colors are important")
• biSizeImage field set to the number of bytes in the image (not including the headers or the palette)
• Resolution set to 0x0 pixels/meter. I'm not sure that's really allowed, but not all images even have meaningful physical resolutions, so leaving the resolution at zero seems reasonable to me.

The rightmost 1/4 of the 16-bpp and higher test images is designed to be visibly different at 15, 16, and 24-bpp bit depths. In the 24-bit color version, every pixel is a slightly different shade of bluish gray. It will appear smooth on a true-color display. The 15- and 16-bit color versions may have a visible "mosaic" effect.

To Do

• The bmpsuite.c program should be able to generate compressed images.
• The bmpsuite.c program should be portable to non-Windows platforms.
• The suite should include some invalid and questionably-valid images, especially files designed to attempt to crash buggy viewers. (The filenames start with "g" meaning "good"; the idea was to create some "bad" files that start with "b", for example.)

By Jason Summers, 4/2001