将UIImage分成两半？

Question

我该如何将一张UIImage图片从中间垂直割开，以便得到两个图片呢？

- Shredder2794

Answer 1

你可以尝试这个：

UIImage *image = [UIImage imageNamed:@"yourImage.png"];
CGImageRef tmpImgRef = image.CGImage;
CGImageRef topImgRef = CGImageCreateWithImageInRect(tmpImgRef, CGRectMake(0, 0, image.size.width, image.size.height / 2.0));
UIImage *topImage = [UIImage imageWithCGImage:topImgRef];
CGImageRelease(topImgRef);

CGImageRef bottomImgRef = CGImageCreateWithImageInRect(tmpImgRef, CGRectMake(0, image.size.height / 2.0,  image.size.width, image.size.height / 2.0));
UIImage *bottomImage = [UIImage imageWithCGImage:bottomImgRef];
CGImageRelease(bottomImgRef);

希望这能对你有所帮助，:)

- xda1001

Answer 2

- (void)splitImage:(UIImage *)image
{
    CGFloat imgWidth = image.size.width/2;
    CGFloat imgheight = image.size.height;

    CGRect leftImgFrame = CGRectMake(0, 0, imgWidth, imgheight);
    CGRect rightImgFrame = CGRectMake(imgWidth, 0, imgWidth, imgheight);

    CGImageRef left = CGImageCreateWithImageInRect(image.CGImage, leftImgFrame);
    CGImageRef right = CGImageCreateWithImageInRect(image.CGImage, rightImgFrame);

    // These are the images we want!
    UIImage *leftImage = [UIImage imageWithCGImage:left];
    UIImage *rightImage = [UIImage imageWithCGImage:right];

    // Don't forget to free the memory!
    CGImageRelease(left);
    CGImageRelease(right);
}

- Durul Dalkanat

---

这是唯一一个不会创建大量上下文的答案。Quartz在优化裁剪过程方面做得非常出色（直接获取图像的像素数据，而不是创建新的上下文、绘制图像，然后裁剪）。当我们将图像分成许多小部分时，这可能快了许多倍！ - Flying_Banana

Answer 3

iOS 11，swift 4.0的更新版本https://stackoverflow.com/users/893872/durul-dalkanat，我认为这是最好的:)

这将图像分成4个部分。

func splitImage(image2D: UIImage) -> [UIImage] {
    let imgWidth = image2D.size.width / 2
    let imgHeight = image2D.size.height / 2
    var imgImages:[UIImage] = []

    let leftHigh = CGRect(x: 0, y: 0, width: imgWidth, height: imgHeight)
    let rightHigh = CGRect(x: imgWidth, y: 0, width: imgHeight, height: imgHeight)
    let leftLow = CGRect(x: 0, y: imgHeight, width: imgWidth, height: imgHeight)
    let rightLow = CGRect(x: imgWidth, y: imgHeight, width: imgWidth, height: imgHeight)

    let leftQH = image2D.cgImage?.cropping(to:leftHigh)
    let rightHQ = image2D.cgImage?.cropping(to:rightHigh)
    let leftQL = image2D.cgImage?.cropping(to:leftLow)
    let rightQL = image2D.cgImage?.cropping(to:rightLow)

    imgImages.append(UIImage(cgImage: leftQH!))
    imgImages.append(UIImage(cgImage: rightHQ!))
    imgImages.append(UIImage(cgImage: leftQL!))
    imgImages.append(UIImage(cgImage: rightQL!))

    return imgImages
}

- user3069232