在iPhone上切割UIImage [英] Slicing up a UIImage on iPhone

问题描述

目标：拍摄UIImage，在中间裁剪一个正方形，将正方形的大小更改为320x320像素，将图像分割为16个80x80图像，将16个图像保存在数组中。

Objective: take a UIImage, crop out a square in the middle, change size of square to 320x320 pixels, slice up the image into 16 80x80 images, save the 16 images in an array.

这里是我的代码：

CGImageRef originalImage, resizedImage, finalImage, tmp;
float imgWidth, imgHeight, diff;
UIImage *squareImage, *playImage;
NSMutableArray *tileImgArray;
int r, c;

originalImage = [image CGImage];

imgWidth = image.size.width;
imgHeight = image.size.height;
diff = fabs(imgWidth - imgHeight);

if(imgWidth > imgHeight){
    resizedImage = CGImageCreateWithImageInRect(originalImage, CGRectMake(floor(diff/2), 0, imgHeight, imgHeight));
}else{
    resizedImage = CGImageCreateWithImageInRect(originalImage, CGRectMake(0, floor(diff/2), imgWidth, imgWidth));
}
CGImageRelease(originalImage);

squareImage = [UIImage imageWithCGImage:resizedImage];      
if(squareImage.size.width != squareImage.size.height){
    NSLog(@"image cutout error!");
    //*code to return to main menu of app, irrelevant here
}else{
    float newDim = squareImage.size.width;
    if(newDim != 320.0){
        CGSize finalSize = CGSizeMake(320.0, 320.0);
        UIGraphicsBeginImageContext(finalSize);
        [squareImage drawInRect:CGRectMake(0, 0, finalSize.width, finalSize.height)];
        playImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }else{
        playImage = squareImage;
    }
}

finalImage = [playImage CGImage];
tileImgArray = [NSMutableArray arrayWithCapacity:0];
for(int i = 0; i < 16; i++){
    r = i/4;
    c = i%4;
    //*
    tmp = CGImageCreateWithImageInRect(finalImage, CGRectMake(c*tileSize, r*tileSize, tileSize, tileSize));
    [tileImgArray addObject:[UIImage imageWithCGImage:tmp]];
}

当原始（可变图像）大于或小于320像素。当它正好是320，结果80x80图像几乎完全是黑色的，一些在边缘有几个像素，可能（我不能真正地告诉）是从原始图像。

The code works correctly when the original (the variable image) has its smaller dimension either bigger or smaller than 320 pixels. When it's exactly 320, the resulting 80x80 images are almost entirely black, some with a few pixels at the edges that may (I can't really tell) be from the original image.

我通过直接显示完整图片进行测试：

I tested by displaying the full image both directly:

[UIImage imageWithCGImage:finalImage];

并且间接：

[UIImage imageWithCGImage:CGImageCreateWithImageInRect(finalImage, CGRectMake(0, 0, 320, 320))];

在这两种情况下，显示都工作。

In both cases, the display worked. The problems only arise when I attempt to slice out some part of the image.

推荐答案

经过一些更多的实验后，我发现了以下解决方案（我仍然不知道为什么它不工作原来写的，虽然。）但无论如何，调整大小后的代码后，切片工作，即使在调整大小是不必要的：

After some more experimentation, I found the following solution (I still don't know why it didn't work as originally written, though.) But anyway, the slicing works after the resize code is put in place even when resizing is unnecessary:

if(newDim != 320.0){
            CGSize finalSize = CGSizeMake(320.0, 320.0);
            UIGraphicsBeginImageContext(finalSize);
            [squareImage drawInRect:CGRectMake(0, 0, finalSize.width, finalSize.height)];
            playImage = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();
}else{
            CGSize finalSize = CGSizeMake(320.0, 320.0);
            UIGraphicsBeginImageContext(finalSize);
            [squareImage drawInRect:CGRectMake(0, 0, finalSize.width, finalSize.height)];
            playImage = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();
}

任何人都有任何线索为什么会这样？

Anyone has any clue WHY this is going on?

PS是的，如果/ else不再需要这里。删除之前我知道它会工作将是愚蠢的，虽然。

P.S. Yes, if/else is no longer required here. Removing it before I knew it was going to work would be stupid, though.

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