Loading BMP Files into QBASIC

[Venom555]

I've done quite a few searches on the internet regarding the loading of a BMP file into QBASIC, but I've either found something quite big or something that does not tell me enough.

Is there any way to just simply load a BMP and let SCREEN 13 find the nearest matching colours?

[Peter Swinkels]

EDIT: See the post following this one for a Quick Basic program that can load bitmaps.

The Quick Basic programs attached to this message can be used to load bitmaps. I think it shouldn't be too hard to figure out how the programs work and how the bitmap format works by studying the code.

Here is some information about the bitmap file format:

Bitmap header:


Location:	Description:
1		2 byte file format indicator: "BM"
19		width in pixels
23		height in pixels
29		bits per pixel
		(1 = monochrome, 4 = 16 colors, 8 = 256 colors, 24 = 24 bit color)
55		If the image uses 24 bit colors the actual image data will start at the location.
		For all other color depths a palette is stored here. The palette is directly followed by the image data.
		The palette contains a 4 byte (of which only the first 3 bytes are used) entry for each color index.
                Each entry contains the RGB values for a specific color index.

[Peter Swinkels]

Here is a program that combines all four of the programs I attached to my previous message. It does a slightly better job at displaying the proper colors in 24 bit bitmaps and checks the file format and encoding. The code needs some cleaning up though and I might add support for RLE and OS/2 encoded bitmaps if I can figure out how these formats work.

Here is an updated table for the bitmap header format:

Bitmap header:

Location:	Description:
1		2 byte file format indicator: "BM"
19		width in pixels
23		height in pixels
29		bits per pixel
		(1 = monochrome, 4 = 16 colors, 8 = 256 colors, 24 = 24 bit color)
31		encoding
		(255 = OS/2, 0 = RGB, 2 = RLE)
55		If the image uses 24 bit colors the actual image data will start at this location.
		For all other color depths a palette is stored here. The palette is directly followed by the image data.
		The palette contains a 4 byte entry (of which only the first 3 bytes are used) for each color index.
                Each entry contains the RGB values for a specific color index.

You can also look at http://www.wotsit.org for information about the bitmap file format.