How to unerase an erased UIImage? - iphone

Question

I am trying an image erasing code in my PanGesture. I am using the code below:
UIImage * image = [UIImage imageNamed:#"326d4fb72362a2e44659141cadfc4977.jpg"];
holderView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 235)];
imgForeground = [[UIImageView alloc] initWithFrame:[holderView frame]];
[imgForeground setImage:image];
[holderView addSubview:imgForeground];
UIPanGestureRecognizer *panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(move:)];
[panRecognizer setMinimumNumberOfTouches:1];
[panRecognizer setMaximumNumberOfTouches:1];
[panRecognizer setDelegate:self];
[holderView addGestureRecognizer:panRecognizer];
[self.view addSubview:holderView];
Then I am handling this here:
-(void)move:(id)sender {
CGPoint currentPoint;
if([(UIPanGestureRecognizer*)sender state] == UIGestureRecognizerStateBegan){
lastPoint = [sender locationInView:imgForeground];
lastPoint.y -=20;
}
else{
currentPoint = [sender locationInView:imgForeground];;
currentPoint.y -=20;
}
UIGraphicsBeginImageContext(imgForeground.frame.size);
[imgForeground.image drawInRect:CGRectMake(imgForeground.frame.origin.x, imgForeground.frame.origin.y, imgForeground.frame.size.width, imgForeground.frame.size.height)];
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineCap(context,kCGLineCapRound); //kCGImageAlphaPremultipliedLast);
CGContextSetLineWidth(context, 10);
CGContextSetRGBStrokeColor(context, 0, 0, 0, 1.0);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeClear);
CGContextBeginPath(context);
CGContextMoveToPoint(context, lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(context, lastPoint.x, lastPoint.y);
CGContextStrokePath(context);
imgForeground.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
How to unerase the same image?

Answer 1

I have the same issue in my app after the long search i found the simple solution for this issue.
i just used touches methods of the UIViewController
The below is the my approach,
Code:-
#pragma mark touches stuff...
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
lastTouch = [touch locationInView:self.editedImageView];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
currentTouch = [touch locationInView:self.editedImageView];
CGFloat brushSize;
if (isEraser)
{
brushSize=eraser;
}
else
{
brushSize=mark;
}
CGColorRef strokeColor = [UIColor whiteColor].CGColor;
UIGraphicsBeginImageContext(self.editedImageView.frame.size);
CGContextRef context = UIGraphicsGetCurrentContext();
[self.editedImageView.image drawInRect:CGRectMake(0, 0, self.editedImageView.frame.size.width, self.editedImageView.frame.size.height)];
CGContextSetLineCap(context, kCGLineCapRound);
CGContextSetLineWidth(context, brushSize);
if (isEraser) {
CGContextSetStrokeColorWithColor(UIGraphicsGetCurrentContext(), [UIColor colorWithPatternImage:self.im].CGColor);
}
else
{
CGContextSetStrokeColorWithColor(context, strokeColor);
CGContextSetBlendMode(context, kCGBlendModeClear);
}
CGContextBeginPath(context);
CGContextMoveToPoint(context, lastTouch.x, lastTouch.y);
CGContextAddLineToPoint(context, currentTouch.x, currentTouch.y);
CGContextStrokePath(context);
self.editedImageView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
lastTouch = [touch locationInView:self.editedImageView];
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
}
The Inputs:
self.editedImageView.image = "Your Custom image";
self.im = "Your Custom image";
The simple solution of your problem will be :-
CGContextSetStrokeColorWithColor(UIGraphicsGetCurrentContext(), [UIColor colorWithPatternImage:self.im].CGColor);
Note:
This not unerase it again drawing the image over
Update:-
self.im = "Your Custom image";
this will be like this....
-(void)eraserConfigure
{
UIImageView *resizeImage=[[[UIImageView alloc]initWithImage:editedImage]autorelease];
/*UIImage */self.im=[UIImage imageFromView:resizeImage scaledToSize:CGSizeMake(self.editedImageView.frame.size.width, self.editedImageView.frame.size.height)];
}

Answer 2

Save a temporary image after every drawing operation.
You should save on temporary files and limit the number of undo operations.