How does QB64 support saving 8bit images?

[CMR]

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

[ahenry3068]

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.

[ahenry3068]

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..  

[Petr]

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.

[CMR]

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