擦除不工作

Question

我绘制线条和任何形状，我想，但在擦除它不工作时，

对于图i用下面的代码

在这个代码我通过使用石英芯

绘制

previousPoint1 = [touch previousLocationInView:m_img]; 
       previousPoint2 = [touch previousLocationInView:m_img]; 
       currentPoint = [touch locationInView:m_img]; 


       // 
       previousPoint2 = previousPoint1; 
       previousPoint1 = [touch previousLocationInView:m_img]; 
       currentPoint = [touch locationInView:m_img]; 
       // calculate mid point 
       CGPoint mid1 = [self midPoint:previousPoint1 :previousPoint2]; 
       CGPoint mid2 =[self midPoint:currentPoint :previousPoint1]; 
       UIGraphicsBeginImageContext(m_img.frame.size); 
       [m_img.image drawInRect:CGRectMake(0, 0, m_img.frame.size.width, m_img.frame.size.height)]; 
       CGContextRef context = UIGraphicsGetCurrentContext(); 
       CGContextMoveToPoint(context, mid1.x, mid1.y); 
       // Use QuadCurve is the key 
       CGContextAddQuadCurveToPoint(context, previousPoint1.x, previousPoint1.y, mid2.x, mid2.y); 
       CGBitmapContextGetColorSpace(context); 



       //CGContextSetStrokeColor(<#CGContextRef context#>, <#const CGFloat *components#>) 
       CGContextSetStrokeColorWithColor(context, color.CGColor); 
       CGContextSetLineCap(context, kCGLineCapRound); 
       CGContextSetLineWidth(context,m_width); 
       CGContextStrokePath(context); 
       m_img.image = UIGraphicsGetImageFromCurrentImageContext(); 
       UIGraphicsEndImageContext(); 

和用于擦除图i用下面的代码

  m_widthString=[userdefault valueForKey:@"EraserWidth"]; 
      m_width=[m_widthString floatValue]; 
      previousPoint1 = [touch previousLocationInView:m_img]; 
      previousPoint2 = [touch previousLocationInView:m_img]; 
      currentPoint = [touch locationInView:m_img]; 
      previousPoint2 = previousPoint1; 
      previousPoint1 = [touch previousLocationInView:m_img]; 
      currentPoint = [touch locationInView:m_img]; 
      // calculate mid point 
      CGPoint mid1 = [self midPoint:previousPoint1 :previousPoint2]; 
      CGPoint mid2 =[self midPoint:currentPoint :previousPoint1]; 
      UIGraphicsBeginImageContext(m_img.frame.size); 
      [m_img.image drawInRect:CGRectMake(0, 0, m_img.frame.size.width, m_img.frame.size.height)]; 

      CGContextRef context = UIGraphicsGetCurrentContext(); 
      CGContextSetStrokeColorWithColor(context, [[UIColor clearColor] CGColor]); 
      CGContextSetFillColorWithColor(context, [[UIColor clearColor] CGColor]); 
      CGContextSetBlendMode(context, kCGBlendModeClear); 
      CGContextSetLineCap(context, kCGLineCapRound); 
      CGContextSetLineWidth(context,m_width); 
      CGContextMoveToPoint(context, mid1.x, mid1.y); 
      CGContextAddQuadCurveToPoint(context, previousPoint1.x, previousPoint1.y, mid2.x, mid2.y); 
      CGContextDrawPath(context, kCGPathFillStroke); 
      m_img.image = UIGraphicsGetImageFromCurrentImageContext(); 
      UIGraphicsEndImageContext(); 

同时删除我改变混合模式清晰，即使它不工作

，但不工作，请帮我

Answer 1

擦除u必须采取trasferent图像视图 和使用CGContextSetBlendMode（背景下，kCGBlendModeClear）; 其正在为我工​​作...