如何在 iOS 中裁剪大图像的中心部分？

Question

当从中心裁剪图像时，裁剪图像将采用源图像的纵横比，但根据我的要求，纵横比会随着新的裁剪尺寸而变化。

我想获得具有新纵横比的图像的确切中心部分。例如，大图像的大小为 (320*480)，然后我想裁剪大小为 (100,100) 的图像的中心部分，纵横比也将是100*100，无需外白或外黑，画质高。

裁剪功能：

- (UIImage *)cropImage:(UIImage*)image andFrame:(CGRect)rect {

    //Note : rec is nothing but the image frame which u want to crop exactly.

    rect = CGRectMake(rect.origin.x*image.scale,
                      rect.origin.y*image.scale,
                      rect.size.width*image.scale,
                      rect.size.height*image.scale);

    CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], rect);
    UIImage *result = [UIImage imageWithCGImage:imageRef
                                          scale:image.scale
                                    orientation:image.imageOrientation];
    CGImageRelease(imageRef);
    return result;
}

请帮助我。

Answer 1

这可能会运行

- (UIImage *)imageByCroppingImage:(UIImage *)image toSize:(CGSize)size
{
    // not equivalent to image.size (which depends on the imageOrientation)!
    double refWidth = CGImageGetWidth(image.CGImage);
    double refHeight = CGImageGetHeight(image.CGImage);

    double x = (refWidth - size.width) / 2.0;
    double y = (refHeight - size.height) / 2.0;

    CGRect cropRect = CGRectMake(x, y, size.height, size.width);
    CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], cropRect);

    UIImage *cropped = [UIImage imageWithCGImage:imageRef scale:0.0 orientation:self.imageOrientation];
    CGImageRelease(imageRef);

    return cropped;
}

Answer 2

var imageView = UIImageView()

// height and width values corresponds to rectangle height and width

imageView  = UIImageView(frame: CGRectMake(0, 0, width, height ))
imageView.image = UIImage(named: "Your Image Name")

// by   setting   content  mode  to  .ScaleAspectFill   image centrally  fill  in   imageView. image   might appear beyond  image frame.

imageView.contentMode = .ScaleAspectFill


// by   setting .clipsToBouds to true,  image set to image frame.

imageView.clipsToBounds = true
view.addSubview(imageView)

Answer 3

// 处理这段代码

     -(UIImage *)croppedImage
    {
    UIImage *myImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    [self.bezierPath closePath];
    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0.0, 0.0, 0.0, 0.0);
    _b_image = self.bg_imageview.image;
    CGSize imageSize = _b_image.size;
    CGRect imageRect = CGRectMake(0, 0, imageSize.width, imageSize.height);
    UIGraphicsBeginImageContextWithOptions(imageSize, NO, [[UIScreen mainScreen] scale]);
    [self.bezierPath addClip];
    [_b_image drawInRect:imageRect];

    UIImage *croppedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
return croppedImage;

}

Answer 4

根据图像计算裁剪矩形

float imgHeight = 100.0f; //Any according to requirement
float imgWidth = 100.0f; //Any according to requirement
CGRect cropRect = CGRectMake((largeImage.size.width/2)-(imgWidth/2),largeImage.size.height/2)-(imgHeight/2),imgWidth,imgHeight);

现在裁剪它

CGImageRef imageRef = CGImageCreateWithImageInRect([largeImage CGImage], cropRect);
// or use the UIImage wherever you like
UIImage *croppedImg = [UIImage imageWithCGImage:imageRef]]; 
CGImageRelease(imageRef);