pixmap trouble...

Ok ok I read all the threads present in the forum about pixmap, something is clear now, but I have a problem with this

'test copy image
Graphics 640,480


Global load_image:TPixmap=LoadPixmap("gfx/world_2.png")
If load_image.format<>PF_RGBA8888 Then load_image=ConvertPixmap( load_image,PF_RGBA8888 )

Copy(load_image)


Flip
WaitKey
End


Function Copy(pix:TPixmap)
Local pix_dest:TPixmap=CreatePixmap(pix.width,pix.height,PF_RGBA8888)
Local psource:Byte Ptr
Local pdest:Byte Ptr
psize=32*4*pix.height

For k=0 To pix.width-32 Step 32
		psource=PixmapPixelPtr(pix,k,0)
		'pdest=PixmapPixelPtr(pix_Dest,pix.width-k,0)
		pdest=PixmapPixelPtr(pix_Dest,k,0)
		MemCopy(pdest,psource,psize)
	
Next

'only for test
image=ConvertToImage(pix_dest)
DrawImage image,0,0
End Function

Function ConvertToImage:timage(pix:TPixmap)
	Local size_x:Int=pix.width
	Local size_y:Int=Pix.height
	Local pdest:Byte Ptr
	Local psource:Byte Ptr
	psource=PixmapPixelPtr(pix,0,0)
	Local psize:Int=size_x*size_y*4 '4 bytes per pixel assuming RGBA8888 format pixmap
	temp_image:TImage=CreateImage(size_x,size_y,1,iflags|DYNAMICIMAGE) 'create dummy image in case we want to do realtime conversion between pixmaps and images/textures
	temp_pixmap:TPixmap=LockImage(temp_image,0,False,True) 'Lock our dummy image so we can draw to it
	pdest=PixmapPixelPtr(temp_pixmap,0,0) 'Set our destination pointer to the image's pixmap
	MemCopy(pdest,psource,psize) 'Copy the pixels from the pixmap in memory to the image/texture's pixmap
	UnlockImage(temp_image) 'Let the image be rendered now
	Return temp_image
End Function

The goal is copy from a pixmap to another one...
Why I get only a black image?

If you want to copy a pixmap then why not use copypixmap?
mypix2:TPixmap=copypixmap(mypix1)
If you want to load a pixmap into an image then image:TImage=loadimage(mypix)

I need to 'dismantle' an image into another image (or pixmap) copying only a small piece/slice of the original in different position.
I already know Copy & Paste method of pixmap but why my example doesn't work?

I do something similar here
Might be because psize isn't big enough? This seems to work...

Graphics 640,480


Global load_image:TPixmap=LoadPixmap("max.png")
If load_image.format<>PF_RGBA8888 Then load_image=ConvertPixmap( load_image,PF_RGBA8888 )

Copy(load_image)


Flip
WaitKey
End


Function Copy(pix:TPixmap)
Local pix_dest:TPixmap=CreatePixmap(pix.width,pix.height,PF_RGBA8888)
Local psource:byte Ptr
Local pdest:byte Ptr
psize=32*4*pix.height*4
For k=0 To pix.width-32 Step 32
		psource=PixmapPixelPtr(pix,k,0)
		pdest=PixmapPixelPtr(pix_Dest,k,0)
		MemCopy(pdest,psource,psize)

Next

image:TImage=LoadImage(pix_DEST)
DrawImage IMAGE,0,0
End Function

Load your pixmap
Create a StaticPixmap or use PixmapWindow to `look at an area of that pixmap`

You now have a pixmap which contains only the area that you wanted. If you want to take that area and instead of it being shared memory with the whole original pixmap, put it into its own pixmap, then create a new pixmap the size of the area and use that pixmaps pixmap.paste() method. You don't have to go copying every single individual pixel yourself.

An alternative is to use ReadPixel() and WritePixel() in your loops.

Oh thanks very much!

Yeah, the pixmap window and paste methods are very useful and should be better publicized...