使用UIKit製作簡單的繪圖應用程序

我在製作繪圖應用程序。我想爲這樣透明的PNG文件着色http://www.not1.xpg.com.br/wp-content/uploads/2011/04/imagens-disney-colorir-mickey.gif 使用UIKit製作簡單的繪圖應用程序

但是我想以這樣的方式進行着色，以便在對它們着色時黑線不會消失。

而且當我使用橡皮擦時，橡皮擦不應該抹去黑線，應該清除顏色而不是畫白色。

我該如何解決這些問題？任何幫助將非常感激。

直到現在我已經完成了。

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
{  
    mouseSwiped = NO; 
    UITouch *touch = [touches anyObject]; 
    lastPoint = [touch locationInView:self.view]; 
} 

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

    mouseSwiped = YES; 
    UITouch *touch = [touches anyObject]; 
    CGPoint currentPoint = [touch locationInView:self.view]; 

    UIGraphicsBeginImageContext(self.view.frame.size); 
    [self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)]; 
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y); 
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y); 
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); 
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush); 
    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, 1.0); 
    CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeNormal); 

    CGContextStrokePath(UIGraphicsGetCurrentContext()); 
    self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext(); 
    [self.tempDrawImage setAlpha:opacity]; 
    UIGraphicsEndImageContext(); 

    lastPoint = currentPoint; 
} 

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

    if(!mouseSwiped) 
    { 
     UIGraphicsBeginImageContext(self.view.frame.size); 
     [self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)]; 
     CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); 
     CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush); 
     CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, opacity); 
     CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y); 
     CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y); 
     CGContextStrokePath(UIGraphicsGetCurrentContext()); 
     CGContextFlush(UIGraphicsGetCurrentContext()); 
     self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext(); 
     UIGraphicsEndImageContext(); 
    } 

    UIGraphicsBeginImageContext(self.mainImage.frame.size); 
    [self.mainImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) blendMode:kCGBlendModeNormal alpha:1.0]; 
    [self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) blendMode:kCGBlendModeNormal alpha:opacity]; 
    self.mainImage.image = UIGraphicsGetImageFromCurrentImageContext(); 
    self.tempDrawImage.image = nil; 
    UIGraphicsEndImageContext(); 
}

來源

2012-11-28 Rahul Gupta

「與此類似」 - 什麼是「this」？ – jimpic

對不起，我忘了提及它。我指的是這個。 http://www.raywenderlich.com/18840/how-to-make-a-simple-drawing-app-with-uikit –

您可能正在談論透明度/ alpha值。繪畫時可以使用特定的顏色來完成所有這些。要擦除，請使用[UIColor clearColor]，如果要「畫出不消失的黑線」，請使用alpha值小於1的顏色。例如[UIColor colorWithRed:1 green:0 blue:0 alpha:0.5]會在現有內容上繪製半透明紅線。

來源

2012-11-28 09:10:12 jimpic

使用UIKit製作簡單的繪圖應用程序

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