Quartz2D会制图片定位

由于Quartz2D坐标系统Y轴方向是向上的，所以为了不使图片倒立，要对CTM（current transformation matrix）进行变换，其中最重要的就是

1 CGContextScaleCTM(context, 1.0, -1.0);

就是将Y轴到过来，此外还可以进行平移、缩放和旋转，但是经过多次变换以后，最终的显示位置往往和初衷不一致，需要反复的调整。因此我就封装了一个这样的函数，可以比较方便的进行图形绘制。

 1 - (void)drawImage:(UIImage*)image 
 2         inContext:(CGContextRef)context 
 3        leftBottom:(CGPoint)leftTop 
 4             scale:(CGFloat)scale 
 5            rotate:(CGFloat)degree
 6 {
 7     CGContextSaveGState(context);
 8     CGContextTranslateCTM(context, 0, self.bounds.size.height);
 9     CGContextScaleCTM(context, 1.0, -1.0);
10     CGContextTranslateCTM(context, leftTop.x, self.bounds.size.height-leftTop.y);
11     if (scale != 1) 
12     {
13         CGContextScaleCTM(context, scale, scale);
14     }
15     if(degree != 0)
16     {
17         CGContextRotateCTM(context, degree);
18     }
19     CGRect newRect = CGRectMake(0, 0, image.size.width, image.size.height);
20     CGContextDrawImage(context, newRect, [image CGImage]);
21     CGContextRestoreGState(context);
22 }

调用代码

 1 - (void)drawRect:(CGRect)rect
 2 {
 3     CGContextRef context = UIGraphicsGetCurrentContext();
 4     UIImage *image = [UIImage imageNamed:@"test.jpg"];
 5     [self drawImage:image inContext:context leftBottom:CGPointMake(0, 90) scale:0.5 rotate:0];
 6     [self drawImage:image inContext:context leftBottom:CGPointMake(160, 130) scale:0.6 rotate:0];
 7     [self drawImage:image inContext:context leftBottom:CGPointMake(160, 130) scale:0.7 rotate:-M_PI/3];
 8     [self drawImage:image inContext:context leftBottom:CGPointMake(160, 130) scale:0.8 rotate:-M_PI/3*2];
 9     [self drawImage:image inContext:context leftBottom:CGPointMake(160, 130) scale:0.9 rotate:-M_PI];
10     [self drawImage:image inContext:context leftBottom:CGPointMake(120, 416) scale:1.0 rotate:0];
11 }

实现效果

posted @ 2012-06-17 22:34  iTenric  阅读(406)  评论(0)    收藏  举报