Convert image to 8bit 256 colors (windows only)

srod · Post by **srod** » Mon Dec 15, 2008 10:19 am

pant pant drool drool hubba hubbaa woof woof........

Aye, and the girl's not bad either!

I think this is another instance when that Sparkie fella start's worring!

Seriously; some excellent work here netty. Great stuff.

djes · Post by **djes** » Mon Dec 15, 2008 10:36 am

Great! This is how "levels" works (one of the most useful photoshop's tool). It creates an histogram of used colours, and you can see how colours are used in the picture, to adjust them accordingly to your perception, the black and white points, and so on.
Now it's time for dithering

Post by **Rings** » Mon Dec 15, 2008 12:25 pm

great work!!

Coolman · Post by **Coolman** » Mon Dec 15, 2008 2:28 pm

There is an error message:

'Ligne 188 :ArraySize() is not a function, array, macro or linked list'

Add this :

; Author: freak (updated for PB 4.00 by Deeem2031)
Procedure ArraySize(*Array)
ProcedureReturn PeekL(*Array-8)
EndProcedure

great work

However, IrfanView is more efficient ...

srod · Post by **srod** » Mon Dec 15, 2008 4:47 pm

On PB 4.3, ArraySize() is a native function.

Coolman · Post by **Coolman** » Tue Dec 16, 2008 2:52 pm

srod wrote:On PB 4.3, ArraySize() is a native function.

******************
; Library commands: ImageTo8bit() and Save8bitImage()
; Author: Lloyd Gallant (netmaestro)
; Date: December 12, 2008
; Target OS: Microsoft Windows All
; Target Compiler: PureBasic 4.0 and later
; License: Free, unrestricted, no warranty
******************

I thought it was compatible PureBasic 4.00...

However, good to know, I never used a beta version of PureBasic

netmaestro · Post by **netmaestro** » Wed Dec 17, 2008 4:01 am

-Fixed a bug where some images were being rendered upside down

-Modified the adaptive colortable routine to avoid placing duplicate entries in the color table

-Removed some small memory leaks

Code is updated in the first post.

srod · Post by **srod** » Wed Dec 17, 2008 11:41 am

netmaestro wrote:-Fixed a bug where some images were being rendered upside down

Interested to see how you fixed that part!

Had decided that the best way was to retrieve the DIB bits first as there seems to be no simple way of getting a hold of a valid bitmapinfoheader structure for the original DIB etc. I think you've just confirmed my supposition!

Again, great code.

netmaestro · Post by **netmaestro** » Wed Dec 17, 2008 1:16 pm

Yes, the trick is to get the DIBits in the same format that you're going to set them. I was taking a shortcut and just feeding SetDIBits the pointer from the object but I see now that you can't do that. The quality difference between this and the professional programs seems to be in the lack of dithering. I have no idea how to do dithering but I'll research it and give it a go. Any thoughts or suggestions on approach would be most appreciated.

djes · Post by **djes** » Wed Dec 17, 2008 2:07 pm

netmaestro wrote:Yes, the trick is to get the DIBits in the same format that you're going to set them. I was taking a shortcut and just feeding SetDIBits the pointer from the object but I see now that you can't do that. The quality difference between this and the professional programs seems to be in the lack of dithering. I have no idea how to do dithering but I'll research it and give it a go. Any thoughts or suggestions on approach would be most appreciated.

http://en.wikipedia.org/wiki/Floyd-Steinberg_dithering

LCD · Post by **LCD** » Sun Jan 04, 2009 1:45 am

Great work! The MSX2 Palette is excellent for ordered dither (I included it in my Retro-X), because you can dither 3, 3 and 2 Bits (8, 8 and 4 levels) and join the bits together.
The adaptive palette calculation is something I was looking for, for the Sprinter 2000 picture conversion.

Blue · Post by **Blue** » Sun Jan 04, 2009 7:57 am

As you say, netmaestro, the adaptive colortable delivers a truly amazing approximation of the original color distribution.
Very nice work and demonstration.

Now waiting for the dithering procedure to clear up the blotches on that poor girl's skin

She must be impatient too...

BTW:
to better compare the original picture with the modified one, i added 3 lines to your example code, just before the Events loop:

Code: Select all

j = hImage
OpenWindow(1,WindowWidth(0)+24,0,ImageWidth(j),ImageHeight(j),"") 
ImageGadget(1,0,0,0,0,ImageID(j))

Michael Vogel · Post by **Michael Vogel** » Sun Jan 04, 2009 9:51 am

Blue wrote: BTW:
to better compare the original picture with the modified one, i added 3 lines to your example code, just before the Events loop:
Code: Select all
j = hImage
OpenWindow(1,WindowWidth(0)+24,0,ImageWidth(j),ImageHeight(j),"") 
ImageGadget(1,0,0,0,0,ImageID(j))

Cool Code, thanks

For even more comfort, you can add some constants...

Code: Select all

#Eight_BlackWhite=0
#Eight_StandardPalette=1
#Eight_AdaptivePalette=2

hImage = LoadImage(#PB_Any, "girl.jpg")
i = ImageTo8bit(hImage, #Eight_AdaptivePalette,0)

and name the windows "8 Bit Picture" and "Original Picture" - because the new picture can look quite similar like the original (because netmaestro did a brilliant job -- once again)

LCD · Post by **LCD** » Mon Jan 05, 2009 1:14 am

Just changed the code a little for testing 16 colours Palette reduction, and it still looks very okay. It can be easy modified to work with almost any number of colours.

netmaestro · Post by **netmaestro** » Sun Aug 30, 2009 8:57 pm

Code is updated to work with PB v4.40, should still be fine with earlier versions of PB.