Question

我正在制作绘图应用。我想为像http://www.not1.xpg.com.br/wp-content/uploads/2011/04/imagens-disney-colorir-mickey.gif

这样透明的PNG文件着色

但是我想以这样的方式着色，这样黑色线条在我上色时就不会消失。

而且当我使用橡皮擦时，橡皮擦不应该擦除黑色线条，应该清除颜色而不是绘制白色。

我该如何解决这些问题？任何帮助将不胜感激。

直到现在我已经做到了。

- (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();
}

Answer 1

您可能正在谈论透明度/ alpha值。您可以在绘图时使用特定颜色完成所有这些操作。要进行删除，请使用[UIColor clearColor]，如果您想“在不消失的情况下绘制黑线”，请使用Alpha值低于1的颜色。例如，[UIColor colorWithRed:1 green:0 blue:0 alpha:0.5]会在现有内容上方绘制半透明的红线

使用UIKit制作一个简单的绘图应用程序

1 个答案: