чертеж стирания, который сохраняется в другом представлении изображения Xcode

Question

Я использую следующий код, чтобы нарисовать изображение с помощью UITouch. Это прекрасно работает, и я сохраняю изображение из временного изображения в другое изображение, когда я иду. Проблема в том, что я хочу вернуться и удалить часть чертежа из сохраненного imageView. Я знаю, что я могу установить цвет в белый цвет, и он будет стирать его, но я рисую поверх другого изображения, содержащего изображение из моего рулона камеры. поэтому мне нужно полностью очистить сохраненный чертеж.

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
{ 



    self.RealImage.frame = CGRectMake(14-(ax2*subtract),138-(ay2*subtract),740*see,850*see); 

    self.imageView.frame = CGRectMake(14-(ax2*subtract),138-(ay2*subtract),740*see,850*see); 

    self.tempImage.frame = CGRectMake(14-(ax2*subtract),138-(ay2*subtract),740*see,850*see); 



    ctr = 0; 
    UITouch *touch = [touches anyObject]; 
    pts[0] = [touch locationInView:self.tempImage]; 

    lastPoint = [touch locationInView:tempImage]; 
} 


- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event 
{ 


    self.RealImage.frame = CGRectMake(14-(self.zoom),138-(self.first),740*see,850*see); 

    self.imageView.frame = CGRectMake(14-(self.zoom),138-(self.first),740*see,850*see); 

    self.tempImage.frame = CGRectMake(14-(self.zoom),138-(self.first),740*see,850*see); 


    UITouch *touch = [touches anyObject]; 
    CGPoint p = [touch locationInView:self.tempImage]; 
    currentPoint = [touch locationInView:tempImage]; 
    ctr++; 
    pts[ctr] = p; 

    if (ctr == 4) 
    { 
     pts[3] = CGPointMake((pts[2].x + pts[4].x)/2.0, (pts[2].y + pts[4].y)/2.0); // move the endpoint to the middle of the line joining the second control point of the first Bezier segment and the first control point of the second Bezier segment 
     [path moveToPoint:pts[0]]; 
     [path addCurveToPoint:pts[3] controlPoint1:pts[1] controlPoint2:pts[2]]; // add a cubic Bezier from pt[0] to pt[3], with control points pt[1] and pt[2] 

     [self draw2]; 


     // replace points and get ready to handle the next segment 
     pts[0] = pts[3]; 
     pts[1] = pts[4]; 
     ctr = 1; 
    } 
    NSLog(@"ctr:%d",ctr); 
    lastPoint = currentPoint; 
} 



- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event 
{ 

    king = pencilString; 

    [path removeAllPoints]; 
    ctr = 0; 



    UIGraphicsBeginImageContext(self.tempImage.frame.size); 
    self.RealImage.frame = CGRectMake(14-(self.zoom),138-(self.first),740*see,850*see); 

    self.imageView.frame = CGRectMake(14-(self.zoom),138-(self.first),740*see,850*see); 

    self.tempImage.frame = CGRectMake(14-(self.zoom),138-(self.first),740*see,850*see); 
    [self.imageView.image drawInRect:CGRectMake(0,0, self.imageView.frame.size.width, self.imageView.frame.size.height) blendMode:kCGBlendModeNormal alpha:1.0]; 
    [self.tempImage.image drawInRect:CGRectMake(0,0, self.tempImage.frame.size.width, self.tempImage.frame.size.height) blendMode:kCGBlendModeNormal alpha:1.0]; 

    self.imageView.image = UIGraphicsGetImageFromCurrentImageContext(); 
    self.tempImage.image = nil; 
    if (see ==2) { 


    self.RealImage.frame = CGRectMake(14-(self.zoom),138-(self.first),1480,1700); 

    self.imageView.frame = CGRectMake(14-(self.zoom),138-(self.first),1480,1700); 

     self.tempImage.frame = CGRectMake(14-(self.zoom),138-(self.first),1480,1700);} 


    UIGraphicsEndImageContext(); 



} 

- (void)draw2 
{ 



    self.RealImage.frame = CGRectMake(14-(self.zoom),138-(self.first),740*see,850*see); 

    self.imageView.frame = CGRectMake(14-(self.zoom),138-(self.first),740*see,850*see); 

    self.tempImage.frame = CGRectMake(14-(self.zoom),138-(self.first),740*see,850*see); 
    UIGraphicsBeginImageContext(self.tempImage.frame.size); 
    [self.tempImage.image drawInRect:CGRectMake(0, 0, self.tempImage.frame.size.width, self.tempImage.frame.size.height)]; 

    pts[3] = CGPointMake((pts[2].x + pts[4].x)/2.0, (pts[2].y + pts[4].y)/2.0); // move the endpoint to the middle of the line joining the second control point of the first Bezier segment and the first control point of the second Bezier segment 
    [path moveToPoint:pts[0]]; 
    [path addCurveToPoint:pts[3] controlPoint1:pts[1] controlPoint2:pts[2]]; // add a cubic Bezier from pt[0] to pt[3], with control points pt[1] and pt[2] 

// вот где я пытаюсь создать стиранию, но все, что я получить его черную линию

if ([pencilString isEqualToString:@"clear2"]) { 

     mode = DrawingModePen; 
     if (mode == DrawingModePen) { 
      NSLog(@"drawing"); 
      CGContextSetStrokeColorWithColor(UIGraphicsGetCurrentContext(), [[UIColor clearColor 
                       ] CGColor]); 
     } 

     UIGraphicsBeginImageContext(self.imageView.frame.size); 



     [self.imageView.image drawInRect:CGRectMake(0, 0, self.imageView.frame.size.width, self.imageView.frame.size.height)]; 
     CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y); 

    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y); 

     self.imageView.image = UIGraphicsGetImageFromCurrentImageContext(); 
     [self.imageView setAlpha:1.0]; 

     [path stroke]; 

     CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeCopy); 
      } 
    else if ([pencilString isEqualToString:@"red"]) { 
     [[UIColor colorWithRed:255.0/255.0 green:0.0 blue:0.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"blue"]) { 
     [[UIColor colorWithRed:51.0/255.0 green:76.0/255.0 blue:255.0/255.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"yellow"]) { 
     [[UIColor colorWithRed:255.0/255.0 green:255.0/255.0 blue:0.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"orange"]) { 
     [[UIColor colorWithRed:255.0/255.0 green:90.0/255.0 blue:0.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"green"]) { 
     [[UIColor colorWithRed:0.0 green:204.0/255.0 blue:0.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"purple"]) { 
     [[UIColor colorWithRed:153.0/255.0 green:0.0 blue:255.0/255.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"redOrange"]) { 
     [[UIColor colorWithRed:255.0/255.0 green:51.0/255.0 blue:0.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"yellowOrange"]) { 
     [[UIColor colorWithRed:255.0/255.0 green:153.0/255.0 blue:0.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"blueViolet"]) { 
     [[UIColor colorWithRed:102.0/255.0 green:51.0/255.0 blue:255.0/255.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"blueGreen"]) { 
     [[UIColor colorWithRed:0.0 green:153.0/255.0 blue:204.0/255.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"redViolet"]) { 
     [[UIColor colorWithRed:255.0/255.0 green:0.0 blue:153.0/255.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"yellowGreen"]) { 
     [[UIColor colorWithRed:204.0/255.0 green:255.0/255.0 blue:0.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"white"]) { 
     [[UIColor whiteColor] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"ltGray"]) { 
     [[UIColor colorWithRed:204.0/255.0 green:204.0/255.0 blue:204.0/255.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"dkGray"]) { 
     [[UIColor colorWithRed:102.0/255.0 green:102.0/255.0 blue:102.0/255.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"brown"]) { 
     [[UIColor colorWithRed:102.0/255.0 green:51.0/255.0 blue:51.0/255.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"tan"]) { 
     [[UIColor colorWithRed:255.0/255.0 green:204.0/255.0 blue:102.0/255.0 alpha:1.0] setStroke]; 
    } 

    else if ([pencilString isEqualToString:@"black"]) { 
     [[UIColor blackColor] setStroke]; 
    } 

    [path stroke]; 

    CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeNormal); 

    // CGContextStrokePath(UIGraphicsGetCurrentContext()); 
    self.tempImage.image = UIGraphicsGetImageFromCurrentImageContext(); 
    [self.tempImage setAlpha:1.0]; 
    self.RealImage.frame = CGRectMake(14-(self.zoom),138-(self.first),740*see,850*see); 

    self.imageView.frame = CGRectMake(14-(self.zoom),138-(self.first),740*see,850*see); 

    self.tempImage.frame = CGRectMake(14-(self.zoom),138-(self.first),740*see,850*see); 

    UIGraphicsEndImageContext(); 



} 

Answer 1

Я понял это. Я поместил оператор if для стирания «clear2» в начале - (void) draw2 {переписав его, сделав мой рисунок на imageView и имея blendMode - kCGBlendModeCopy. Затем я просто помещаю все остальное в инструкцию else, и это работает.
Вот код.

- (void)draw2 
{ 

if ([pencilString isEqualToString:@"clear2"]) { 

    UIGraphicsBeginImageContext(imageView.frame.size); 
    [[UIColor clearColor] setStroke]; 
    [imageView.image drawInRect:CGRectMake(0,0,imageView.frame.size.width, imageView.frame.size.height)]; 




    CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeCopy); 



    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y); 

    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y); 

    CGContextStrokePath(UIGraphicsGetCurrentContext()); 

    [path setLineWidth:20.0]; 


     [path stroke]; 


imageView.image = UIGraphicsGetImageFromCurrentImageContext(); 



} 
else { 

UIGraphicsBeginImageContext(self.tempImage.frame.size); 
[self.tempImage.image drawInRect:CGRectMake(0, 0, self.tempImage.frame.size.width, self.tempImage.frame.size.height)]; 

pts[3] = CGPointMake((pts[2].x + pts[4].x)/2.0, (pts[2].y + pts[4].y)/2.0); // move the endpoint to the middle of the line joining the second control point of the first Bezier segment and the first control point of the second Bezier segment 
[path moveToPoint:pts[0]]; 
[path addCurveToPoint:pts[3] controlPoint1:pts[1] controlPoint2:pts[2]]; // add a cubic Bezier from pt[0] to pt[3], with control points pt[1] and pt[2] 




if ([pencilString isEqualToString:@"red"]) { 
    [[UIColor colorWithRed:255.0/255.0 green:0.0 blue:0.0 alpha:1.0] setStroke]; 
    [path setLineWidth:10.0*see]; 
} 
[path stroke]; 

CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeNormal); 

// CGContextStrokePath(UIGraphicsGetCurrentContext()); 
self.tempImage.image = UIGraphicsGetImageFromCurrentImageContext(); 
[self.tempImage setAlpha:1.0]; 


UIGraphicsEndImageContext(); 
} 


} 

Answer 2

Вы можете назвать этот метод в любом месте.

- (void)eraseLine 
{ 

    UIGraphicsBeginImageContext(self.bounds.size); 

    [self.viewImage drawInRect:self.bounds]; 

    CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeClear); 

    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); 
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), lineWidth); 
    CGContextBeginPath(UIGraphicsGetCurrentContext()); 
    CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeClear); 
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), previousPoint.x, previousPoint.y); 
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y); 

    CGContextStrokePath(UIGraphicsGetCurrentContext()); 
    self.viewImage = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 
    previousPoint = currentPoint; 

    [self setNeedsDisplay]; 

}