Tiling a timage to another Timage.

To get around images not divisable by 4, you need to check to make sure, that the pixel are not outside the pixmap.

Function round:Float(n:Float) 
	Local r:Float = n Mod 2.0
	If r >=.5
		Return Ceil(n) 
	Else
		Return Floor(n) 
	EndIf
End Function

Function ditherfilter:timage(source:TImage, brush:TImage) 
	Local sourcePixmap:TPixmap = LockImage(source) 
	Local sourcePixmapPtr:Byte Ptr = PixmapPixelPtr(sourcePixmap, 0, 0) 
	Local tmpPixmap:TPixmap = CopyPixmap(sourcePixmap) 
	Local tmpPixmapPtr:Byte Ptr = PixmapPixelPtr(tmpPixmap,0,0)
	Local x:Int,y:Int

	Local w:Int = tmpPixmap.width
	Local h:Int = tmpPixmap.height
	Local extra_width:Float = w - (Floor(w / 4) * 4) 
	Local extra_height:Float = h - (Floor(h / 4) * 4) 
	For x = 0 To w - 1 Step 4' this is a 4 pixel jump thgouth the image
		For y = 0 To h - 1 Step 4 ' this is a 4 pixel jump thgouth the image
			' set the component totals to be averaged upon completion
			Local total_red:Float = 0
			Local total_green:Float = 0
			Local total_blue:Float = 0
			Local pixels_scanned:Float = 0
			Local gray:Float = 0
			Local subimage:Float = 0
			'average the color of each 4x4 square
			For Local x2:Int = 0 To 3
				If x+x2 < w Then
					For Local y2:Int = 0 To 3
						If y+y2 < h Then
							' get the color of each pixel of 16
							Local red:Float = sourcePixmapPtr[(x + x2) * 4 + (y + y2) * 4 * w] 
							Local green:Float = sourcePixmapPtr[(x + x2) * 4 + (y + y2) * 4 * w + 1] 
							Local blue:Float = sourcePixmapPtr[(x + x2) * 4 + (y + y2) * 4 * w + 2] 
							total_red:+red
							total_green:+green
							total_blue:+blue
							pixels_scanned:+1
						End If
					Next
				End If
			Next
			
			'draw the 4x4 fill
			total_red:/pixels_scanned
			total_green:/pixels_scanned
			total_blue:/pixels_scanned
			gray = (total_red + total_green + total_blue) / 3
			For Local x2:Int = 0 To 3
				If x+x2 < w Then
					For Local y2:Int = 0 To 3
						If y+y2 < h Then
							subimage = round(gray / 255 * 16) 
							Local brush:TPixmap = LockImage(brush, subimage, 0, 0) 
							Local brushPixmapPtr:Byte Ptr = PixmapPixelPtr(brush, 0, 0) 
							Local w2:Int = brush.width
							tmpPixmapPtr[(x + x2) * 4 + (y + y2) * 4 * w] = brushPixmapPTr[x2 * 4 + y2 * 4 * w2] 
							tmpPixmapPtr[(x + x2) * 4 + (y + y2) * 4 * w + 1] = brushPixmapPTr[x2 * 4 + y2 * 4 * w2 + 1] 
							tmpPixmapPtr[(x + x2) * 4 + (y + y2) * 4 * w + 2] = brushPixmapPTr[x2 * 4 + y2 * 4 * w2 + 2]            		'alpha
						End If
					Next
				End If
			Next
		Next
	Next
	Local tmpImage:TImage = LoadImage(tmpPixmap)
	Return tmpImage
End Function