如何在iPhone上旋转Quartz绘制的文本 [英] How to rotate text drawn by Quartz on iPhone

问题描述

我想用Quartz绘制一些文本。现在，该应用程序将获得
alt text http://www.freeimagehosting.net/uploads/ 71a84c9b49.png ，但我希望它显示为0123456789。有没有办法显示它的正常方向？

I want to draw some texts using Quartz. Now the app draws alt text http://www.freeimagehosting.net/uploads/71a84c9b49.png, but I want it to show as "0123456789". Is there any way to show its normal orientation?

这是我的代码：

    //set image view
 drawImage = [[UIImageView alloc] initWithImage:nil];
 drawImage.frame = self.view.frame;
 [self.view addSubview:drawImage];

 UIGraphicsBeginImageContext(self.view.frame.size);  // begin
 // current context
 CGContextRef context = UIGraphicsGetCurrentContext();

 CGContextSelectFont(context, "Courier", 40,  kCGEncodingMacRoman);
 CGFloat white[] = {1.0, 1.0, 1.0, 1.0};
 CGContextSetFillColor(context, white);
 CGContextShowTextAtPoint(context, 0, 30, "0123456789", strlen("0123456789"));

 // get image
 drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
 UIGraphicsEndImageContext();    // end

推荐答案

在Quartz中，图像将是上升因为它的Y轴是倒置的。

In Quartz, the image will be upside down because its Y-Axis is inverted.

iPhone的Y轴从上到下呈正值，即原点位于左上角，而在Quartz和OpenGL中，坐标与良好的旧几何相同，即原点在左下角。

iPhone's Y axis goes positive from top to bottom i.e. origin is at top left while in Quartz and OpenGL, the co-ordinates are the same way as good old geometry i.e. origin at bottom left.

以下是解决Quartz反演问题的一些代码：

Here is some code for solving Quartz inversion problem:

CGContextRef ctx = UIGraphicsGetCurrentContext();
// Tanslate and scale upside-down to compensate for Quartz's inverted coordinate system
CGContextTranslateCTM(ctx, 0.0, rect.size.height);
CGContextScaleCTM(ctx, 1.0, -1.0);

这是一篇有趣的帖子，作者说新加坡的一个团队放弃了一个iPhone项目到期这个他们无法弄清楚的倒置问题： http://trandangkhoa.blogspot.com/2009/07/iphone-os-drawing-image-and-stupid.html

Here is an interesting post about it where the author says a team in Singapore gave up an iPhone project due to this inversion problem which they could not figure out: http://trandangkhoa.blogspot.com/2009/07/iphone-os-drawing-image-and-stupid.html

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