How does QB64 support saving 8bit images?

How does QB64 support saving 8bit images? - Printable Version

+- QB64 Phoenix Edition (https://qb64phoenix.com/forum)
+-- Forum: QB64 Rising (https://qb64phoenix.com/forum/forumdisplay.php?fid=1)
+--- Forum: Code and Stuff (https://qb64phoenix.com/forum/forumdisplay.php?fid=3)
+---- Forum: Help Me! (https://qb64phoenix.com/forum/forumdisplay.php?fid=10)
+---- Thread: How does QB64 support saving 8bit images? (/showthread.php?tid=3640)

How does QB64 support saving 8bit images? - CMR - 04-27-2025

I've tried loading a 32 bit image and saving it as an 8bit image, but it doesn't seem to work. Image editors like Graphics Gale can't seem to open it, and when I try to reload it that fails also.

Code: (Select All)



''Test loading a 32bit image and saving it to 8 bit

Option _Explicit



Screen _NewImage(320,240,256)



Dim img32& : img32& = _LoadImage("img32.png", 256)

Dim img8bit& : img8bit& = _NewImage(64, 64, 256)

_PutImage (0,0),img32&, img8bit&



_SaveImage "img8bit.bmp", img8bit&

_FreeImage(img32&)

_FreeImage(img8bit&)



Sleep

End

checking the image:

Code: (Select All)



''Load and check an image

Dim img8& : img8& = _LoadImage("img8bit&.bmp", 256)



Screen _NewImage(320, 240, 256)



_PutImage (0,0), img8&



_FreeImage(img8&)

sleep

end

RE: How does QB64 support saving 8bit images? - ahenry3068 - 04-27-2025

For one thing your file name in the 2nd code block is incorrect.

I don't particularly like the Dithering that QB64PE produces for 8 bit images anyway. I would have probably done this with a **SHELL** command to ImageMagick.

RE: How does QB64 support saving 8bit images? - ahenry3068 - 04-27-2025

Code: (Select All)

Option _Explicit



Screen _NewImage(320, 240, 256)



Dim img32&: img32& = _LoadImage("img32.png")

Dim img8bit&: img8bit& = _NewImage(640, 617, 256)

_PutImage (0, 0), img32&, img8bit&



_SaveImage "img8bit.bmp", img8bit&

_FreeImage (img32&)

_FreeImage (img8bit&)



Sleep

End

This worked for me..

RE: How does QB64 support saving 8bit images? - Petr - 04-27-2025

I would just like to point out that the built-in QB64PE dithering provides better results if you load a 32-bit image with the LoadImage command with parameter 257 instead of parameter 256. Then the visual appearance is very similar to the original.

RE: How does QB64 support saving 8bit images? - CMR - 04-27-2025

(04-27-2025, 02:59 AM)ahenry3068 Wrote: For one thing your file name in the 2nd code block is incorrect.

I don't particularly like the Dithering that QB64PE produces for 8 bit images anyway. I would have probably done this with a **SHELL** command to ImageMagick.

You know, that might actually be a thing. Big Grin

I need to stop posting at night. It's all auto complete's fault.