objective-c：在UIImage或UIImageView上绘制线条 [英] objective-c: draw line on top of UIImage or UIImageView

问题描述

如何在UIImage或UIImageView上绘制一条简单的线？

How do I draw a simple line on top of a UIImage or UIImageView?

推荐答案

以下代码的工作原理是创建一个新图像与原始图像大小相同，将原始图像的副本绘制到新图像上，然后沿新图像的顶部绘制1像素线。

The following code works by creating a new image the same size as the original, drawing a copy of the original image onto the new image, then drawing a 1 pixel line along to the top of the new image.

// UIImage *originalImage = <the image you want to add a line to>
// UIColor *lineColor = <the color of the line>

UIGraphicsBeginImageContext(originalImage.size);

// Pass 1: Draw the original image as the background
[originalImage drawAtPoint:CGPointMake(0,0)];

// Pass 2: Draw the line on top of original image
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 1.0);
CGContextMoveToPoint(context, 0, 0);
CGContextAddLineToPoint(context, originalImage.size.width, 0);
CGContextSetStrokeColorWithColor(context, [lineColor CGColor]);
CGContextStrokePath(context);

// Create new image
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

// Tidy up
UIGraphicsEndImageContext();

或者，您可以将该行创建为 CAShapeLayer 然后将其作为子视图添加到 UIImageView （参见这个答案）。

Alternatively, you could create the line as a CAShapeLayer then add it as a subview to the UIImageView (see this answer).

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