如何使用路径提取UIImage?
我需要将路径内的内容转换为新的UIImage。我需要的是旋转矩形的内容。这是我用来获取矩形角的代码。 (x,y =图像中心。宽度,图像高度)。
UIBezierPath* aPath = [UIBezierPath bezierPath];
//1
[aPath moveToPoint:CGPointMake(
x+(width/2)*cosf(A)-(height/2)*sinf(A),
y+(height/2)*cosf(A)+(width/2)*sinf(A))];
NSLog(@"%f, %f", x+(width/2)*cosf(A)-(height/2)*sinf(A),
y+(height/2)*cosf(A)+(width/2)*sinf(A));
//2
[aPath moveToPoint:CGPointMake(
x-(width/2)*cosf(A)-(height/2)*sinf(A),
y+(height/2)*cosf(A)-(width/2)*sinf(A))];
NSLog(@"%f, %f", x-(width/2)*cosf(A)-(height/2)*sinf(A),
y+(height/2)*cosf(A)-(width/2)*sinf(A));
//3
[aPath moveToPoint:CGPointMake(
x-(width/2)*cosf(A)+(height/2)*sinf(A),
y-(height/2)*cosf(A)-(width/2)*sinf(A))];
NSLog(@"%f, %f", x-(width/2)*cosf(A)+(height/2)*sinf(A),
y-(height/2)*cosf(A)-(width/2)*sinf(A));
//4
[aPath moveToPoint:CGPointMake(
x+(width/2)*cosf(A)+(height/2)*sinf(A),
y-(height/2)*cosf(A)+(width/2)*sinf(A))];
NSLog(@"%f, %f", x+(width/2)*cosf(A)+(height/2)*sinf(A),
y-(height/2)*cosf(A)+(width/2)*sinf(A));
//5
[aPath moveToPoint:CGPointMake(
x+(width/2)*cosf(A)-(height/2)*sinf(A),
y+(height/2)*cosf(A)+(width/2)*sinf(A))];
NSLog(@"%f, %f", x+(width/2)*cosf(A)-(height/2)*sinf(A),
y+(height/2)*cosf(A)+(width/2)*sinf(A));
[aPath closePath];
我在想这样的话:A picture of the problem. (这里的形状不同。)我希望黄色部分成为新的UIImage。
答案 0 :(得分:3)
使用UIBezierPath
作为剪切路径。有addClip
方法。
有关详细信息,请参阅the Quartz2D Programming Guide,尤其是this part。
我们的想法是创建一个新的Bitmap上下文,使用你的路径应用剪辑,然后在这个位图上下文中绘制图像(这将被剪裁),最后从中生成一个UIImage。
此外,您应该自行创建一个CGRect
而不进行任何轮换,而不是自己动一些数学来旋转您想要用于裁剪的CGRect
,并使用CGAffineTransform
旋转它。这样就可以避免使用cos
/ sin
函数自行进行计算,并使代码更易于阅读。
[编辑]以下是一个完整的例子:
我确实检查了它并且像魅力一样。
// Generate a UIBezierPath of a rounded rect rotated by angle radians
-(UIBezierPath*)computePathWithRect:(CGRect)rect
cornerRadius:(CGFloat)cornerRadius
angle:(CGFloat)radians;
{
// Compute basic path
UIBezierPath* path = [UIBezierPath bezierPathWithRoundedRect:rect cornerRadius:cornerRadius];
// Apply rotation.
// Don't forget that rotations are around origin 0,0 so if you want to rotate around the rect's center,
// you need to apply a translation so that the rect's center is at 0,0, then rotate, and translate it back at its original position.
CGAffineTransform restoreCenterPosition = CGAffineTransformMakeTranslation(CGRectGetMidX(rect), CGRectGetMidY(rect));
CGAffineTransform rotateFromOrigin = CGAffineTransformRotate(restoreCenterPosition,radians);
CGAffineTransform rotateFromRectCenter = CGAffineTransformTranslate(rotateFromOrigin, -CGRectGetMidX(rect), -CGRectGetMidY(rect));
[path applyTransform:rotateFromRectCenter];
return path;
}
// Generate a new image from srcImage but clipped with the given path
-(UIImage*)clipImage:(UIImage*)srcImage withPath:(UIBezierPath*)path
{
UIGraphicsBeginImageContextWithOptions(srcImage.size, NO, 0.0);
// Add clipping path
// Actually UIBezierPath has a method for that, that is equivalent to CGContextClip(currentContext, bezierPath.CGPath), so better use it
[path addClip];
// Flip coordinates before drawing image as UIKit and CoreGraphics have inverted coordinate system
CGContextTranslateCTM(UIGraphicsGetCurrentContext(), 0, srcImage.size.height);
CGContextScaleCTM(UIGraphicsGetCurrentContext(), 1, -1);
// Draw image, that will thus be clipped, on the bitmap context
CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, srcImage.size.width, srcImage.size.height), srcImage.CGImage);
// Generate final (clipped) image
UIImage* clippedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return clippedImage;
}
// Usage example
- (void)doClipping
{
UIImage* originalImage = ...
UIBezierPath* path = [self computePathWithRect:CGRectMake(100,100,184,94)
cornerRadius:10.f
angle:30*M_PI/180.f];
UIImage* clippedImage = [self clipImage:originalImage withPath:path];
self.resultImageView.image = clippedImage;
}