These formats are defined below. Click on the Label/FOURCC to be taken to its definition.
Please see “Bitmap Orientation and biHeight” for important additional information. Also, if you are interested in RGB to YCrCb conversion, you may find this page helpful.
| Label | FOURCC in Hex | Bits per pixel | Description |
| BI_BITFIELDS | 0x00000003 | 16,24,32 | Raw RGB with arbitrary sample packing within a pixel. Packing and precision of R, G and B components is determined by bit masks for each. |
| BI_RGB | 0x00000000 | 1,4,8,16,24,32 | Basic Windows bitmap format. 1, 4 and 8 bpp versions are palettised. 16, 24 and 32bpp contain raw RGB samples. |
| BI_RLE4 | 0x00000002 | 4 | Run length encoded 4bpp RGB image. |
| BI_RLE8 | 0x00000001 | 8 | Run length encoded 8bpp RGB image. |
| raw | 0x32776173 | ? | Apparently “raw, uncompressed RGB bitmaps” but I have no idea how many bits per pixel (uses bpp field in header?) |
| RGB (BI_RGB) |
0x32424752 | 1,4,8,16,24,32 | Alias for BI_RGB |
| RGBA | 0x41424752 | 16,32 | Raw RGB with alpha. Sample precision and packing is arbitrary and determined using bit masks for each component, as for BI_BITFIELDS. |
| RGBT | 0x54424752 | 16,32 | Raw RGB with a transparency field. Layout is as for BI_RGB at 16 and 32 bits per pixel but the msb in each pixel indicates whether the pixel is transparent or not. |
| RLE (BI_RLE4) |
0x34454C52 | 4 | Alias for BI_RLE4 |
| RLE8 (BI_RLE8) |
0x38454C52 | 8 | Alias for BI_RLE8 |
Bayer Data Formats
Recently, a collection of “Bayer” data formats have been registered. These encode images with only a single color sample at each pixel position and are frequently used in acquisition of digital images where the image is captured through a color filter array. It is not clear to me how these formats define the layout of the filter array used but it may be fair to assume that they relate to a commonly used Bayer pattern originally developed by Kodak which has builds an image out of 2×2 blocks containing green samples in the top left and bottom right positions, red in the top right and blue in the bottom left.
Silicon Imaging’s web site offers further explanation here.