在 UIImageView 内移动 UIImage

Move UIImage inside UIImageView(在 UIImageView 内移动 UIImage)

问题描述

我有一个 UIImageView(红色方块)，它将显示一个必须缩放的 UIImage(我可以接收大于或小于 UIImageView 的图像代码>).缩放后，UIImage 的显示部分是它的中心.

I have an UIImageView (red squares) that will display a UIImage that must be scaled (I can receive images greater or smaller that the UIImageView). After scaling it, the showed part of the UIImage is the center of it.

我需要在蓝色方块中显示图像的一部分，我该如何存档?

What I need is to show the part of the image in the blue squares, how can I archive it?

我只能获取图像大小(高度和宽度)，但它显示的是原始大小，而它应该是缩放后的大小.

I'm only able to get the image size (height and width), but it display the original size, when it's supposed to be the scaled one.

self.viewIm = [[UIImageView alloc] initWithFrame:CGRectMake(100, 100, 120, 80)];
self.viewIm.backgroundColor = [UIColor greenColor];
self.viewIm.layer.borderColor = [UIColor redColor].CGColor;
self.viewIm.layer.borderWidth = 5.0;
UIImage *im = [UIImage imageNamed:@"benjen"];
self.viewIm.image = im;
self.viewIm.contentMode = UIViewContentModeScaleAspectFill;
//    self.viewim.clipsToBounds = YES;
[self.view addSubview:self.viewIm];

推荐答案

我在 this answer 上找到了一个很好的近似值.在那之后，类别会调整图像的大小，然后使用中心点进行裁剪.我使用(0,0)作为原点将其调整为裁剪.因为我真的不需要一个类别，所以我将它用作单一方法.

I found a very good approximation on this answer. In that, the category resize the image, and use the center point to crop after that. I adapt it to crop using (0,0) as origin point. As I don't really need a category, I use it as a single method.

- (UIImage *)imageByScalingAndCropping:(UIImage *)image forSize:(CGSize)targetSize {
    UIImage *sourceImage = image;
    UIImage *newImage = nil;
    CGFloat scaleFactor = 0.0;
    CGFloat scaledWidth = targetSize.width;
    CGFloat scaledHeight = targetSize.height;

    if (CGSizeEqualToSize(image.size, targetSize) == NO) {
        if ((targetSize.width / image.size.width) > (targetSize.height / image.size.height)) {
            scaleFactor = targetSize.width / image.size.width; // scale to fit height
        } else {
            scaleFactor = targetSize.height / image.size.height; // scale to fit width
        }

        scaledWidth  = image.size.width * scaleFactor;
        scaledHeight = image.size.height * scaleFactor;
    }

    UIGraphicsBeginImageContext(targetSize); // this will crop

    CGRect thumbnailRect = CGRectZero;
    thumbnailRect.origin = CGPointZero;
    thumbnailRect.size.width  = scaledWidth;
    thumbnailRect.size.height = scaledHeight;

    [sourceImage drawInRect:thumbnailRect];

    newImage = UIGraphicsGetImageFromCurrentImageContext();

    if(newImage == nil) {
        NSLog(@"could not scale image");
    }

    //pop the context to get back to the default
    UIGraphicsEndImageContext();

    return newImage;
}

我的电话是这样的:

self.viewIm = [[UIImageView alloc] initWithFrame:CGRectMake(100, 100, 120, 80)];
self.viewIm.image = [self imageByScalingAndCropping:[UIImage imageNamed:@"benjen"] forSize:CGSizeMake(120, 80)];
[self.view addSubview:self.viewIm];

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