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To me the most unusual characteristic of the BMP format is that the pixel lines are stored in bottom up order. Years ago I wrote a program to convert .IMG scan files produced by WIPS software for a Xerox Datacopy 730 scanner to .PCX run length encoded for file export via floppy diskette. I added support for .BMP and .RLE formats. The first thing I discovered was that the "first" scan line in the .BMP file is the bottom line of pixels in the image (whereas in the .IMG and .PCX format the first scan line in the file is the top line). Naaman Brown (talk) 14:57, 24 September 2009 (UTC)[reply]

The "bottom up" line order I believe may derive from graphics texture mapping which uses the "mathematical" axes having (0,0) bottom left on the graph, so yes the bitmap image format pixel array (and other formats) do not work from the top down. I'm adding this to the main page as I think it's important information which is not obvious. Ah I missed it (it's already added) Grahamatwp (talk) 14:23, 27 May 2023 (UTC)[reply]

http://www.fileformat.info/format/bmp/index.dir

When I was trying to calculate to ensure I fully understand the workings and file structure of the BMP file structure. My calculations are different from what was displayed in the table.

In example 1 At the row 02h offset, I calculated the size of BMP file to be 70 bytes, but it was (64 + 6) not (54 + 16), can I know where did I go wrong with my calculation steps?

Steps: 1. '46 00 00 00' are the hex values 2. 6 * 16⁰ + 4 * 16¹ = 6 + 64

At the row 26h, how was the value 2835 pixels calculated? The formula 72DPI X 39.3701 inches wasn't explained quite clearly. My own calculations gave me 4875 pixels using the steps similar to the one above.

Thank you for your time and help. 210.19.13.180 (talk) 15:17, 22 March 2023 (UTC)[reply]

Is it correct to use the term 'pixel' in the article? I think that a more appropriate term would be 'texel'. After all, a bitmap unit can be displayed in more than one pixel (zoom in) or occupy an area smaller than one pixel (zoom out). 188.47.110.77 (talk) 19:55, 18 August 2024 (UTC)[reply]

The term 'texel' only applies to texture mapping. Most BMP files are not used in that way, so 'pixel' is correct. MrOllie (talk) 20:02, 18 August 2024 (UTC)[reply]

The article says that XBM and XPM are similar formats. They really are not. Windows bit maps are binary formats. You'll need a hex editor or hexdump to see the data in them. XBM and XPM are actually plain text files that can be opened in any text editor. They are formatted as a C header file that can be included in a C source file. PPM and PBM are also plain text files. 173.189.8.8 (talk) 21:30, 8 October 2024 (UTC)[reply]