bmp decoder on amospro

DiabloV · 12 January 2023, 06:01

[SOLVED] I'm looking to make a bmp decoder on amospro. I'm looking at the structures of the bmp file, but I can't find the right information to read all the data where it is needed.

Dan · 12 January 2023, 16:01

Here is a source code of a bitmap reader in QBasic (pc/dos) http://petesqbsite.com/sections/tuto...ding_bmps.html

paraj · 12 January 2023, 18:07

Be aware that BMP files are little endian, and the image is usually stored upside down. Assuming you want to read an 8-bit BMP for most of them you can just read the width/height pair as 32-bit little endian longs starting from offset 18 ($12, so height at $16). Palette is at offset 54 ($36) and stored as 256 32-bit little endian longs as xxRRGGBB (i.e. bytes are BB GG RR xx). The image data follows that, but upside down from nearly every other image format. True color (24/32-bit) BMPs don't have a palette, but here the pixels are also stored BGR.

The format allows for a lot of flexibility, but the above is enough as long as you only need to support files you create yourself. I haven't programmed in amos, so I can't write the function for you, but if you have some code that doesn't work I can probably spot any errors (as long as they relate to the format)

DiabloV · 22 July 2023, 08:23

hello. I have SOLVED This. i have self-made my routine decoder

12 January 2023, 06:01	#1
DiabloV Registered User Join Date: Jan 2021 Location: FRANCE Posts: 30	bmp decoder on amospro [SOLVED] I'm looking to make a bmp decoder on amospro. I'm looking at the structures of the bmp file, but I can't find the right information to read all the data where it is needed. Last edited by DiabloV; 22 July 2023 at 08:23.

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12 January 2023, 16:01	#2
Dan Registered User Join Date: Nov 2004 Location: Germany Posts: 629	Here is a source code of a bitmap reader in QBasic (pc/dos) http://petesqbsite.com/sections/tuto...ding_bmps.html

12 January 2023, 18:07	#3
paraj Registered User Join Date: Feb 2017 Location: Denmark Posts: 1,098	Be aware that BMP files are little endian, and the image is usually stored upside down. Assuming you want to read an 8-bit BMP for most of them you can just read the width/height pair as 32-bit little endian longs starting from offset 18 ($12, so height at $16). Palette is at offset 54 ($36) and stored as 256 32-bit little endian longs as xxRRGGBB (i.e. bytes are BB GG RR xx). The image data follows that, but upside down from nearly every other image format. True color (24/32-bit) BMPs don't have a palette, but here the pixels are also stored BGR. The format allows for a lot of flexibility, but the above is enough as long as you only need to support files you create yourself. I haven't programmed in amos, so I can't write the function for you, but if you have some code that doesn't work I can probably spot any errors (as long as they relate to the format)

22 July 2023, 08:23	#4
DiabloV Registered User Join Date: Jan 2021 Location: FRANCE Posts: 30	hello. I have SOLVED This. i have self-made my routine decoder

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