cocos2d for iPhone

A fast, easy to use, free, and community supported 2D game engine

1. 

   jonathan0382
   Member

   Hi all,

   Quick question, hopefully easy to answer.

   I have a ccrendertexture that I'm drawing on with a brush. I need to be able to pick a point on the ccrendertexture (target) and return whether it is opaque or not.

   I must be a spaz, or am just coding waaaay too late into the night, but I can't get it. Any suggestions?

   Thanks,

   Jonathan0382

   Posted 1 year ago #
2. 

   jonathan0382
   Member

   Ok, I tried the following: grabbing the buffer data as a UIImage and then checking the opacity of the pixel at the location:

   -(BOOL) checkOpacityAtLocation:(CGPoint) _location
   {
   	UIImage *bufferImage = [target getUIImageFromBuffer];	
   
   	int width = (int)bufferImage.size.width;
   	int height = (int)bufferImage.size.height;
   
   	CFDataRef imageData = CGDataProviderCopyData(CGImageGetDataProvider(bufferImage.CGImage));
   	const UInt32 *pixels = (const UInt32*)CFDataGetBytePtr(imageData);
   
   	int j = ((480-_location.y) * width) + _location.x;
   
   	if (pixels[j] & 0xff000000){
   		return NO;
   	} else {
   		return YES;
   	}
   
   	CFRelease(imageData);
   }

   This works, but is ridiculously slow. Does anyone know a quicker way to do this, or have any suggestions?

   Thanks in advance.

   jonathan0382

   Posted 1 year ago #
3. 

   araker
   Moderator

   You could try glReadPixels and put it at the begin or end of your update method to minimize the render stall.

   Posted 1 year ago #
4. 

   jonathan0382
   Member

   Nice. Thanks araker.

   Byte pixelColor[4];
   glReadPixels(_location.x,_location.y, 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, &pixelColor[0]);

   and then check pixelColor[i] for i=0,1,2 to get the color, and pixelColor[3] to get opacity.

   So, how do I apply this to only the CCRenderTexture?

   Thanks

   :D

   Posted 1 year ago #

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