Create an image on a blank canvas

BlitzMax Forums/BlitzMax Programming/Create an image on a blank canvas

AlternativeRealities

(Posted 2008) [#1]

I'm hoping that someone will be able to help me with a query on images in BlitzMax.

What I want to do is create a new image and paste another onto it. The code I'm currently using I've cribbed from this forum but it seems to allow black pixels to become transparent, which I don't want. How can I adapt this code to paste a picture into a larger black picture?

Function InsertImage:timage(src:TImage,destx:Int,desty:Int,srcFrame:Int,dest:TImage)
Local dmap:TPixmap = LockImage(dest)
Local smap:TPixmap = LockImage(src,srcFrame)
		
For y=0 To dest.height-1
For x=0 To dest.width-1
WritePixel(dmap,x,y,$0:Int)
Next
Next
				
For y:Int =0 To ImageHeight(src)-1
For x:Int=0 To ImageWidth(src)-1
color:Int = ReadPixel(smap,x,y)
			
color=(color & ($FFFFFF:Int)) | $FF000000:Int
pixX=x+destX
pixY=y+desty
err=0
If pixX<0 Or pixX>dest.width-1
err=1
End If
If pixY<0 Or pixY>dest.height-1
err=1
End If
If err=0 							WritePixel(dmap,x+destx,y+desty,color)				
End If
				
Next
Next
UnlockImage(src,srcFrame)
UnlockImage(dest)
Return dest
End Function

Thanks in advance.

tonyg

(Posted 2008) [#2]

Easy option is to draw them then grab them or use pixmap paste method

ima747

(Posted 2008) [#3]

http://www.blitzmax.com/Community/posts.php?topic=74153

The lower code sample is the one to get as it has some bugs fixed

Might be of use depending on exactly what you're going for. It's very straight forward and easy to modify, I've torn it to bits to suit my needs but now mine will draw one image on another with a replace color for white if I need, or blank areas with a mask graphic, and will set empty pixels for white for alpha blending so they don't get blacked out.

if you're using the alpha feature then I would recommend changing the alpha blend portion to

sourceR = (1 - (sourceA/255)) * destR + (sourceA/255) * sourceR
sourceG = (1 - (sourceA/255)) * destG + (sourceA/255) * sourceG
sourceB = (1 - (sourceA/255)) * destB + (sourceA/255) * sourceB

as it wasn't working correctly for me as

sourceR = (sourceR * light * sourceA / AlphaSum) + destA / AlphaSum * (destR * destA / AlphaSum) 
sourceG = (sourceG * light * sourceA / AlphaSum) + destA / AlphaSum * (destG * destA / AlphaSum) 
sourceB = (sourceB * light * sourceA / AlphaSum) + destA / AlphaSum * (destB * destA / AlphaSum)

I didn't use the light feature so I chopped that you, but you could add it back in if you wanted it...

tonyg

(Posted 2008) [#4]

or use pixmap paste method..

Graphics 800,600
Local mypix1:TPixmap = LoadPixmap("max.png")
Local mypix2:TPixmap = LoadPixmap("player1.png")
mypix1.paste(mypix2,0,0)
Local myimage:timage=LoadImage(mypix1)
While Not KeyHit(KEY_ESCAPE)
   Cls
   DrawImage myimage,0,0
   Flip
Wend