Cocos2d: pixel perfect collision for batched sprites - ios

Question

I found a pixel perfect collision algorithm developed by Daniel Vilchez and included in a project shared in this cocos2d-iphone.org forum topic.
Below there is the part of the algorithm I am interested. I am trying to modify this because whenever I used CCRenderTexture, as originally in the code, the App crashed.
I am thinking of alternative methods based on circle collision but those are "not pixel perfect" and in the case my bullet is a wave with this shape it wouldn't work well.
**I am wondering how can I get the algorithm working with sprites batched in a CCSpriteBatchNode? And if so does this strictly include the usage of CCRenderTexture? **
To be precise, this question is partially related to this other question of mine, on creating an instance of CCRenderTexture that causes my App to crash. I post two different ones because here I am asking about the algorithm, in the other one I just ask why CCRenderTexture causes my App to crash (without using Daniel's pixel perfect algorithm, but just creating an instance of CCRenderTexture).
Adapted CODE (here is missing CCRenderTexture because it made my app crashing, so I commented out the usage of _rt - instance of CCRenderTexture). The code does not work properly, so I guess I need CCRenderTexture and hence I asked the question:
-(BOOL) isPixelPerfectCollisionBetweenSpriteA:(CCSprite*)spr1 spriteB:(CCSprite*) spr2
{
BOOL isCollision = NO;
CGRect intersection = CGRectIntersection([spr1 boundingBox], [spr2 boundingBox]);
// Look for simple bounding box collision
if (!CGRectIsEmpty(intersection))
{
// Get intersection info
unsigned int x = intersection.origin.x;
unsigned int y = intersection.origin.y;
unsigned int w = intersection.size.width;
unsigned int h = intersection.size.height;
unsigned int numPixels = w * h;
//NSLog(#"\nintersection = (%u,%u,%u,%u), area = %u",x,y,w,h,numPixels);
// Draw into the RenderTexture
//[_rt beginWithClear:0 g:0 b:0 a:0];
// Render both sprites: first one in RED and second one in GREEN
glColorMask(1, 0, 0, 1);
[spr1 visit];
glColorMask(0, 1, 0, 1);
[spr2 visit];
glColorMask(1, 1, 1, 1);
// Get color values of intersection area
ccColor4B *buffer = malloc( sizeof(ccColor4B) * numPixels );
glReadPixels(x, y, w, h, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
//[_rt end];
// Read buffer
unsigned int step = 1;
for(unsigned int i=0; i<numPixels; i+=step)
{
ccColor4B color = buffer[i];
if (color.r > 0 && color.g > 0)
{
isCollision = YES;
break;
}
}
// Free buffer memory
free(buffer);
}
return isCollision;
EDIT: I found also KKPixelMaskSprite but it doesn't seem to work for high resolution sprites batched in CCSpriteBatchNodes (see comment here).