iphone：将纹理应用于CGContextStrokePath [英] iphone: Apply a texture to CGContextStrokePath

问题描述

我在StackOverflow中搜索所有问题和答案，但无法得到我想要的结果。我想使用PNG文件，在用户触摸和移动点显示为笔划。这是PNG文件：

I search all the question and answer in StackOverflow but can not get the result I want. I would like to use a PNG file, to display as a stroke at the point user touch and move. This is the PNG file:

但我在StackOverflow上做了所有的方法，即使使用CGPatternRef，但我没有我想要的结果。我得到的结果是：

But I did all the ways on StackOverflow, even using CGPatternRef, but I don't have the result I want. The result I have is here:

但我想要的结果是：

这个结果我在OpenGL ES中完成了，但我不能在Core Graphics中做到这一点。我想我可以在每个点使用CGContextDrawImage，但这种方式导致性能不佳，因为我必须在用户触摸的2点之间绘制所有点的图像。我想你以前遇到过这个问题。你认为我可以在Core Graphics中应用纹理来绘制这样的笔画吗？非常感谢。

This result I have done in OpenGL ES, but I can not do that in Core Graphics. I think I can use CGContextDrawImage at each point, but this way cause poor performance because I must draw image all the points between 2 points user touched. I think you have encountered this problem before. Do you think I can apply the texture to draw stroke like this in Core Graphics? I am very appreciated.

推荐答案

使用模式创建线条时，它看起来像第一个图像，而不是第二。该线条简单地是您提供的纹理图像的平铺，将其裁剪成线条的形状。没有办法知道你想要将圆圈合并在一起看起来像一条实线。为此你应该只用一个纯黑色的线。

When you create a line using a pattern it is going to look like the first image, not the second. The line is simply a tiling of the texture image you provide cropped out into the shape of a line. There is no way for it to know that you meant to merge the circles together to look like a solid line. For that you should probably just make a line with a solid black color.

对于任何试图在第一张图片中实现图案线条的人来说，有一个很好的教程解释如何在此处执行此操作： http://blog.robertturrall.com/tag/cgcontextsetstrokepattern/

For anyone trying to achieve the patterned line in the first image there is an excellent tutorial explaining how to do this here: http://blog.robertturrall.com/tag/cgcontextsetstrokepattern/

基本上你需要的是：

// first define the pattern width and height
const float kPatternWidth = 8;
const float kPatternHeight = 8;

void DrawPatternCellCallback(void *info, CGContextRef cgContext) 
{
    // Create a CGImage and use CGContextDrawImage() to draw it into the graphics context provided by the callback function.
    UIImage *patternImage = [UIImage imageNamed:@"yourtextureimage.png"];
    CGContextDrawImage(cgContext, CGRectMake(0, 0, kPatternWidth, kPatternHeight), patternImage.CGImage);
}

确保void周围没有括号。还要确保DrawPatternCellCallback部分在drawRect之前出现，否则它将无效。

Make sure "void" has no parentheses around it. Also make sure the DrawPatternCellCallback part comes before drawRect or it won't work.

然后你的drawRect需要以下内容：

Then your drawRect needs the following:

- (void)drawRect:(CGRect)rect {
    CGContextRef ctx = UIGraphicsGetCurrentContext();

    const CGRect patternBounds = CGRectMake(0, 0, kPatternWidth, kPatternHeight);
    const CGPatternCallbacks kPatternCallbacks = {0, DrawPatternCellCallback, NULL};

    CGAffineTransform patternTransform = CGAffineTransformIdentity;
    CGPatternRef strokePattern = CGPatternCreate(
                                             NULL,
                                             patternBounds,
                                             patternTransform,
                                             kPatternWidth, // horizontal spacing
                                             kPatternHeight, // vertical spacing
                                             kCGPatternTilingNoDistortion,
                                             true,
                                             &kPatternCallbacks);
    CGFloat color1[] = {1.0, 1.0, 1.0, 1.0};

    CGColorSpaceRef patternSpace = CGColorSpaceCreatePattern(NULL);
    CGContextSetStrokeColorSpace(ctx, patternSpace);
    CGContextSetStrokePattern(ctx, strokePattern, color1);
    CGContextSetLineWidth(ctx, 4.0);
    CGContextDrawPath(ctx);

    // If you aren't using ARC:
    CGPatternRelease(strokePattern);
    strokePattern = NULL;
    CGColorSpaceRelease(patternSpace);
    patternSpace = NULL;
}

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