根据自己给定的frame对图片进行裁剪
scale 图片的缩放比例
rect 要裁剪的frame 不能超出原图
返回裁剪后的图片
(UIImage )ct_imageFromImage:(UIImage )image inRect:(CGRect)rect {
CGFloat scale = 1 ;CGRect rect2 = CGRectMake(rect.origin.x * scale, rect.origin.y * scale, scale rect.size.width, scale rect.size.height);
CGImageRef cgImg = CGImageCreateWithImageInRect(image.CGImage, rect2);
UIImage *clippedImg = [UIImage imageWithCGImage:cgImg];
CGImageRelease(cgImg);
return clippedImg;
}