Creating a BMP file (bitmap) in C

Question

I\'m trying to make a bitmap in C, just from code. I\'m currently trying to make a very easy .bmp image, with a height of 1px and a width of 4 pixels, with all white pixels.

Answer 1

Your pixel offset (bytes 10..13) is zero, but the pixel data don't actually start at the beginning of the file, they start at byte 54.

Also:

• Your comment on byte 34 says "bits" but means "bytes", but of course that doesn't matter.

• Your horizontal and vertical resolutions have the wrong byte order, but I very much doubt that that matters.

If I were doing this I'd define structs for the header data (indeed, if you're on Windows, Microsoft have already done this) and use a macro or something for putting bytes into the right order portably.

Whether you "have to reverse the order of the bytes" depends on the endianity of the processor you're using. Writing separate bytes separately, as you're doing, is an effective way to avoid having to worry about this.