Cocos2d 2.0 - Ignoring touches to transparent areas of layers/sprites - cocos2d-iphone

Question

I have an app where I have several layers created from PNG images with transparency. These layers are all on the screen over each other. I need to be able to ignore touches given to transparent areas of layers and just be able to detect as touches, when the user taps on a non-transparent area of a layer... see pic...
How do I do that? thanks.

Answer 1

Here you have a possible solution.
Implement an extension on CCLayer and provide this method:
- (BOOL)isPixelTransparentAtLocation:(CGPoint)loc
{
//Convert the location to the node space
CGPoint location = [self convertToNodeSpace:loc];
//This is the pixel we will read and test
UInt8 pixel[4];
//Prepare a render texture to draw the receiver on, so you are able to read the required pixel and test it
CGSize screenSize = [[CCDirector sharedDirector] winSize];
CCRenderTexture* renderTexture = [[CCRenderTexture alloc] initWithWidth:screenSize.width
height:screenSize.height
pixelFormat:kCCTexture2DPixelFormat_RGBA8888];
[renderTexture begin];
//Draw the layer
[self draw];
//Read the pixel
glReadPixels((GLint)location.x,(GLint)location.y, kHITTEST_WIDTH, kHITTEST_HEIGHT, GL_RGBA, GL_UNSIGNED_BYTE, pixel);
//Cleanup
[renderTexture end];
[renderTexture release];
//Test if the pixel's alpha byte is transparent
return (pixel[3] == 0);
}

Answer 2

if Lio's solution doesn't work, you may add add transparent sprite as a child you yours, place it just under your non-transparent area with size of this non-tranparent area and resive all touches by this new transparent sprite, but not by original sprite.

Answer 3

Here is my solution to your requirement, let me know if it works or not
Create a Category on CCMenu with Name Transparent
File CCMenu+Tranparent.h
#import "CCMenu.h"
#interface CCMenu (Transparent)
#end
File CCMenu+Tranparent.m
#import "CCMenu+Transparent.h"
#import "cocos2d.h"
#implementation CCMenu (Transparent)
-(CCMenuItem *) itemForTouch: (UITouch *) touch{
CGPoint touchLocation = [touch locationInView: [touch view]];
touchLocation = [[CCDirector sharedDirector] convertToGL: touchLocation];
CCMenuItem* item;
CCARRAY_FOREACH(children_, item){
UInt8 data[4];
// ignore invisible and disabled items: issue #779, #866
if ( [item visible] && [item isEnabled] ) {
CGPoint local = [item convertToNodeSpace:touchLocation];
/*
TRANSPARENCY LOGIC
*/
//PIXEL READING 1 PIXEL AT LOCATION
CGRect r = [item rect];
r.origin = CGPointZero;
if( CGRectContainsPoint( r, local ) ){
if([NSStringFromClass(item.class) isEqualToString:NSStringFromClass([CCMenuItemImage class])]){
CCRenderTexture* renderTexture = [[CCRenderTexture alloc] initWithWidth:item.boundingBox.size.width * CC_CONTENT_SCALE_FACTOR()
height:item.boundingBox.size.height * CC_CONTENT_SCALE_FACTOR()
pixelFormat:kCCTexture2DPixelFormat_RGBA8888];
[renderTexture begin];
[[(CCMenuItemImage *)item normalImage] draw];
data[3] = 1;
glReadPixels((GLint)local.x,(GLint)local.y, 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, data);
[renderTexture end];
[renderTexture release];
if(data[3] == 0){
continue;
}
}
free(data);
return item;
}
}
}
return nil;
}
#end
This will check for pixel for returning the CCMenuItem.
Its working fine here.. let me know if you face any issues
-Paresh Rathod
Cocos2d Lover

Answer 4

The solution that worked great for me was using Sprite sheets. I use TexturePacker to create sprite sheets. Steps to create sprite sheet using TexturePacker:
1. Load all the image (.png) files into TexturePacker.
2. Chose data format as coco2d and choose PVR as the texture format.
3. Load the sprite sheet into your code and extract images from your sprite sheet.
Detailed description can be found here.