Question

我对CoreGraphics很新（虽然我已经做了一段时间的iphone编程）

问题，我有这个按比例缩放的片段，并将UIImage剪辑为圆圈：

-(UIImage *)counterpartImageForSchedule:(Schedule *)counterpartSchedule inSize:(CGSize)size
{
    // This function returns a newImage, based on image, that has been:
    // - scaled to fit in (CGRect) rect
    // - and cropped within a circle of radius: rectWidth/2

    UIImage *image=[UIImage imageNamed:@"fakeuser1.png"];

    // when kendy sends hash, check that this image is not on the cache, otherwise download, clip & stylized
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(size.width, size.height), NO, 0.0);
    CGContextRef context = UIGraphicsGetCurrentContext();


                //Get the width and heights
    CGFloat imageWidth = image.size.width;
    CGFloat imageHeight = image.size.height;
    CGFloat rectWidth = size.width;
    CGFloat rectHeight = size.height;

    //Calculate the scale factor
    CGFloat scaleFactorX = rectWidth/imageWidth;
    CGFloat scaleFactorY = rectHeight/imageHeight;

    if (scaleFactorX>scaleFactorY) {
        scaleFactorY=scaleFactorX;
    } else
    {
        scaleFactorX=scaleFactorY;
    }


    //Calculate the centre of the circle
    CGFloat imageCentreX = rectWidth/2;
    CGFloat imageCentreY = rectHeight/2;

    // Create and CLIP to a CIRCULAR Path
    // (This could be replaced with any closed path if you want a different shaped clip)
    CGFloat radius = rectWidth/2;
    CGContextBeginPath (context);
    CGContextAddArc (context, imageCentreX, imageCentreY, radius, 0, 2*M_PI, 0);


    CGContextClosePath (context);

    CGContextClip (context);

    //Set the SCALE factor for the graphics context
    //All future draw calls will be scaled by this factor
    CGContextScaleCTM (context, scaleFactorX, scaleFactorY);    
    // the stroke

    // Draw the IMAGE
    CGRect myRect = CGRectMake(0, 0, imageWidth, imageHeight);
    [image drawInRect:myRect];

    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();



    return newImage;
}

问题是，我如何描绘我用来剪辑图像的路径（例如，4个像素，黑色或白色）？我需要画一个新的吗？

非常感谢任何帮助！

Answer 1

路径可以是任何其他对象 - 在本例中是CGPath（CGPathRef）。在使用任何路径之前，将其封装为CGPath（在这种情况下，可能是CGMutablePathRef，或者您可以在使用剪辑路径之前调用CGContextCopyPath）。现在您可以重用该路径。

以下是我的一个应用程序中的示例，其中我构建了一个路径，然后将其描边，然后剪切到相同的路径（c是图形上下文）：

CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path, nil, CGRectGetMaxX(r) - radius, ins);
CGPathAddArc(path, nil, 
             radius+ins, radius+ins, radius, -M_PI/2.0, M_PI/2.0, true);
CGPathAddArc(path, nil, 
             CGRectGetMaxX(r) - radius, radius+ins, radius, M_PI/2.0, -M_PI/2.0, true);
CGPathCloseSubpath(path);
CGContextAddPath(c, path);
CGContextSetLineWidth(c, 2);
CGContextStrokePath(c);
CGContextAddPath(c, path);
CGContextClip(c);
CGPathRelease(path);

另一种可能性是使用UIBezierPath - 一个完整的Objective-C对象，而不是CGContext函数。它封装了一个CGPath，你可以重用那个路径 - 剪辑它，然后抚摸它。或者反过来说。

用于剪裁UIImage的iphone笔画路径

1 个答案: