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PODraw clean and smooth free hand drawing with CGContext (alpha + blend)
 

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  1. PODraw clean and smooth free hand drawing with CGContext (alpha + blend)
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    <p>Following is my code for free hand drawing using CGContext. I want to use the color having alpha value 0.6 and the blend mode as <code>kCGBlendModeColor</code>. But while drawing, I get the following effect : the color is overlapping and becomes dark. I want non overlapping and smooth draw. </p> <pre><code> -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; lastTouch = [touch locationInView:self]; } -(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; CGPoint currentTouch = [touch locationInView:self]; CGFloat brushSize = 35; UIColor *color = [UIColor blueColor]; CGFloat red = 0.0, green = 0.0, blue = 0.0, alpha = 0.0; if ([color respondsToSelector:@selector(getRed:green:blue:alpha:)]) { [color getRed:&amp;red green:&amp;green blue:&amp;blue alpha:&amp;alpha]; } else { const CGFloat *components = CGColorGetComponents(color.CGColor); red = components[0]; green = components[1]; blue = components[2]; alpha = components[3]; } UIGraphicsBeginImageContext(self.frame.size); CGContextRef context = UIGraphicsGetCurrentContext(); [self.image drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)]; CGContextSetLineCap(context, kCGLineCapRound); CGContextSetLineWidth(context, brushSize); CGContextSetRGBStrokeColor(context, red, green, blue, 0.6) ; CGContextSetBlendMode(context, kCGBlendModeColor); CGContextBeginPath(context); CGContextMoveToPoint(context, lastTouch.x, lastTouch.y); CGContextAddLineToPoint(context, currentTouch.x, currentTouch.y); CGContextStrokePath(context); self.image = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); lastTouch = [touch locationInView:self]; } </code></pre> <p><img src="https://i.stack.imgur.com/qpzib.png" alt="enter image description here"></p>
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    1. USNikana Reklawyks
    1. USPrerna chavan
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      1. PODraw clean and smooth free hand drawing with CGContext (alpha + blend)
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      1. USPrerna chavan
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    1. COhi prerna,i just give one idea which i implemented in my code, i think you can store whole location point in array and after that when your drawrect method call just check there that the points are already exist in array or not.. if exist then skip the point otherwise add this point and draw line with your main point's array....
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      1. USParas Joshi
    2. COFor that i will have to iterate through the saved points in the array after consistently drawing array will become very large and response will become very slow.
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      1. PODraw clean and smooth free hand drawing with CGContext (alpha + blend)
      1. USPrerna chavan
    3. COok now just see some logic from this tutorial and also download demo if required http://www.bukisa.com/articles/231702_iphone-drawing-over-an-image-part-1
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      1. PODraw clean and smooth free hand drawing with CGContext (alpha + blend)
      1. USParas Joshi
 

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