Cocos2D magnification - making the code dynamic and using an image - ios

Question

I have found the following code and I need help with editing it. I am not really familiar with texture rendering.
First of all, init method takes a rect and magnifies only that area? How can I make it more dynamic and magnify only whatever is underneath the magnifying glass?
Secondly, Is it possible to change the shape to circle rather than rectangle?
Or Can I use an image as the frame of the magnifying glass?
Here is the code..
Cheers..
.h file
#import <Foundation/Foundation.h>
#import "cocos2d.h"
#interface Magnify : CCNode {
BOOL active;
CGRect rect;
CGFloat magnifyScale;
CCNode *renderNode;
CCRenderTexture *renderTexture;
}
- (id)initWithNodeToMagnify:(CCNode *)n rect:(CGRect)rectToMagnify scale:(CGFloat)scale;
- (void)enable;
- (void)disable;
.m file
#import "Magnify.h"
#implementation Magnify
- (id)initWithNodeToMagnify:(CCNode *)n rect:(CGRect)rectToMagnify scale:(CGFloat)scale
{
if (self = [super init]) {
self.visible = active = NO;
renderNode = n;
rect = rectToMagnify;
magnifyScale = scale;
renderTexture = [[CCRenderTexture renderTextureWithWidth:rect.size.width height:rect.size.height] retain];
[self addChild:renderTexture];
}
return self;
}
- (void)enable
{
self.visible = active = YES;
[self scheduleUpdate];
}
- (void)disable
{
self.visible = active = NO;
[self unscheduleUpdate];
}
- (void)drawAreaToTexture
{
[renderTexture beginWithClear:0.0 g:0.0 b:0.0 a:1.0];
// shift the renderNode's position to capture exactly the rect we need
CGPoint originalPosition = renderNode.position;
renderNode.position = ccpSub(originalPosition, rect.origin);
// scale the node as we want
CGFloat originalScale = renderNode.scale;
renderNode.scale = magnifyScale;
[renderNode visit];
// shift renderNode's position back
renderNode.position = originalPosition;
// scale back
renderNode.scale = originalScale;
[renderTexture end];
}
- (void)update:(ccTime)dt
{
[self drawAreaToTexture];
}
- (void)dealloc
{
[renderTexture release];
[super dealloc];
}
#end

Answer 1

OK, so, as I mentioned above for something like this, one possible answer is to use the CCLens3D class to get the "effect" of magnifying something in a circular manner.
I found using this to be a little tricky because it doesn't seem to work unless it's a child of the top level node of your 'scene'.
Here is some code I use to create a lens that moves around the screen, and then disappears:
// Create the lens object first.
//
CCLens3D *lens =
[CCLens3D actionWithPosition:fromPos
radius:50
grid:ccg(50, 50)
duration:2.0];
// Set the "size" of the lens effect to suit your needs.
//
[lens setLensEffect:1.0];
// In my case, I then move the lens to a new position. To apply an action on
// a lens, you need to give the actions to the actionManager in the
// CCDirector instance.
//
CCMoveTo *move = [CCMoveTo actionWithDuration:2.0 position:toPos];
// I had another action in this array, but this will do.
//
CCSequence *seq = [CCSequence actions:move, nil];
// Now tell the actionManager to move the lens. This is odd, but it works.
//
[[[CCDirector sharedDirector] actionManager] addAction:seq target:lens paused:NO];
// Now just for some more weirdness, to actually make the lens appear and operate
// you run it as an action on the node it would normally be a child of. In my case
// 'self' is the CCLayer object that is the root of the current scene.
//
// Note that the first action is the lens itself, and the second is a special
// one that stops the lens (which is a "grid" object).
//
[self runAction:[CCSequence actions:lens, [CCStopGrid action], nil]];
I imagine that you should be able to stop the grid by running the CCStopGrid action when you want to. In my case it is a programmed thing. In yours it might be when the user lets go of a button.