Mask after Load?

BlitzMax Forums/BlitzMax Programming/Mask after Load?

Tibit

(Posted 2004) [#1]

I managed to mask an image if I do it before I loading it but I can't manage to mask an image "on the fly" in the gameloop. The idea I had was to first pick a normal maskcolor(background), then I would pick another color as mask and then paint a rect or something behind my image(Tank). In this way I'll be able to create players/ships/etc with a wide selection of colors. But even thou I use SetBlend(AlphaBlend) or SetBlend(MaskBlend) nothing happens to the image.

'Shouldn't this work?

SetMaskColor 255,255,0
SetBlend(MASKBLEND)
DrawImage Image,BX,BY

tonyg

(Posted 2004) [#2]

I'd be very interested in the answer to this as well.
From another topic it was stated that the maskcolor needs to be determined at loadtime or else a pixmap is required to alter the image (2 pixmaps? 1 of the image and another to mask?)
If true then it's a step backwards.
<edit> sorry, that's a bit harsh.. something that I'd like to see changed.

Tibit

(Posted 2004) [#3]

Yea, I'll check out if pixmaps can change the problem

tonyg

(Posted 2004) [#4]

This is what I came up with...

Graphics 640,480,16
back = LoadImage("back.png")
front = LoadImage("masked.png",dynamicimage)
While Not KeyDown(key_escape)
   If Keydown(key_space)
      burb = 255
   Else 
      burb = 128
   endif
   DrawImage back,100,100
   tg_pixmap = LockImage(front)
   tg1_pixmap = MaskPixmap(tg_pixmap,burb,0,burb)
   UnlockImage(front)
   DrawPixmap tg1_pixmap,100,100
   DrawText "burb : " + burb,0,120
   Flip
   cls
   release tg_pixmap
   release tg1_pixmap
   flushmem
wend
end

where back.png is 100*100 coloured rectangle (in my case 63,175,47) and masked.png is 100*100 coloured rec (223,0,0) with smaller rec of 255,0,255.
If there is a way to copy tg1_pixmap back to a 'normal' image it might do the job.
<edit> for better example.

Tibit

(Posted 2004) [#5]

Great example! It really got me going =)

I figured that you don't really need both tg_pixmap and tg1_pixmap, I used tg_pixmap at both places and it worked fine or am I missing something?

And I have a question, why do you release the pixmap each frame?

My tanks is now running around in different colors =) So it works fine, I used grabimage to get it all together into one image.

It seems like BlitzMax new way to handle images require pixmaps in this way. Still feels a bit strange you can't change the maskcolor after you loaded the image. Anyway if this is the case then I think it should be added to the documentation.

tonyg

(Posted 2004) [#6]

I found the memory increasing so release the pixmaps to keep it under control.
Hmmm.. I get an unhandled exception if I try to use the same pixmap for the lockimage and maskpixmap.
How exactly did you use the same pixmap for both?
I agree that BMX needs to use pixmap as images can not be changed on the fly but it is a shame. B3D had maskimage done quite nicely.
I'm assuming you had to draw the pximap then grabimage to get the new image... is that right? If you found a more elegant way I'd be interested.

Tibit

(Posted 2004) [#7]

Yes I draw it all, then I copy that part to a new image with grabimage.

Graphics 640,480,16
back = LoadImage("back.png")
front = LoadImage("masked.png",dynamicimage)
'back.png is 100*100 coloured rectangle (in my Case 63,175,47) And masked.png is 100*100 coloured rec (223,0,0) with smaller rec of 255,0,255

While Not KeyDown(key_escape)
   If KeyDown(key_space)
      burb = 255
   Else 
      burb = 128
   EndIf
   
   SetColor 0,0,255
   DrawRect 50,50,200,200
   'DrawImage back,100,100
   SetColor 255,255,255
   
   SetColor 0,0,255'color of this tank
   DrawRect 50,50,200,200
   tg_pixmap = LockImage(front)
   tg_pixmap = MaskPixmap(tg_pixmap,burb,0,burb)
   UnlockImage(front)

   DrawPixmap tg_pixmap,100,100
   DrawText "burb : " + burb,0,120

   Flip
   Cls
   Release tg_pixmap
   FlushMem
Wend
End