Question

目标：拍摄UIImage，在中间裁剪出正方形，将正方形尺寸更改为320x320像素，将图像切割成16个80x80图像，将16个图像保存在数组中。

这是我的代码：

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）的较小尺寸大于或小于320像素时，代码可正常工作。当它恰好是320时，生成的80x80图像几乎全部是黑色的，有些像素边缘可能（我无法分辨）可能来自原始图像。

我通过直接显示完整图像进行了测试：

[UIImage imageWithCGImage:finalImage];

间接地：

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

在这两种情况下，显示都有效。只有在我试图切出图像的某些部分时才会出现这些问题。

Answer 1

经过一些更多的实验，我发现了以下解决方案（我仍然不知道为什么它不像最初编写的那样工作。）但是无论如何，即使调整大小，调整大小代码之后的切片也会起作用是不必要的：

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？

P.S。是的，如果此处不再需要/ else。在之前删除它我知道它会起作用将是愚蠢的。

Answer 2

出于好奇，当你知道你要把16件东西放进去的时候，你为什么要制作一个0级的可变数组呢？

除此之外，我已经尝试了用于调整大小和切片的基本技术（我不需要裁剪，因为我正在使用已经是正方形的图像）而且我无法重现你的模拟器中的问题。你可能想尝试将你的代码分成三个独立的函数（裁剪到正方形，调整大小和切成碎片）然后分别测试三个，这样你就可以弄清楚导致问题的三个步骤中的哪一个（即输入图像你已经在普通的图形程序中操作而不是使用目标c，然后检查你得到的东西！）。

我将在下面附加我的调整大小和切片函数的版本，这将有所帮助。让你的版本可以查看是很好的，因为我不需要自己找到所有方法一次。：）

正如笔记所述，提到的二维数组是我自己的类，由NSMutableArrays构建，但您可以轻松实现自己的版本或使用平面NSMutableArray。 ;）

// cut the given image into a grid of equally sized smaller images
// this assumes that the image can be equally divided in the requested increments
// the images will be stored in the return array in [row][column] order
+ (TwoDimensionalArray *) chopImageIntoGrid : (UIImage *) originalImage : (int) numberOfRows : (int) numberOfColumns
{   
// figure out the size of our tiles
int tileWidth = originalImage.size.width / numberOfColumns;
int tileHeight = originalImage.size.height / numberOfRows;

// create our return array
TwoDimensionalArray * toReturn = [[TwoDimensionalArray alloc] initWithBounds : numberOfRows 
                                                                             : numberOfColumns];

// get a CGI image version of our image
CGImageRef cgVersionOfOriginal = [originalImage CGImage];

// loop to chop up each row
for(int row = 0; row < numberOfRows ; row++){
    // loop to chop up each individual piece by column
    for (int column = 0; column < numberOfColumns; column++)
    {
        CGImageRef tempImage = 
                CGImageCreateWithImageInRect(cgVersionOfOriginal, 
                                             CGRectMake(column * tileWidth, 
                                                        row * tileHeight, 
                                                        tileWidth, 
                                                        tileHeight));
        [toReturn setObjectAt : row : column : [UIImage imageWithCGImage:tempImage]];
    }
}

// now return the set of images we created
return [toReturn autorelease];
}

// this method resizes an image to the requested dimentions
// be a bit careful when using this method, since the resize will not respect
// the proportions of the image
+ (UIImage *) resize : (UIImage *) originalImage : (int) newWidth : (int) newHeight
{   
// translate the image to the new size
CGSize newSize = CGSizeMake(newWidth, newHeight); // the new size we want the image to be
UIGraphicsBeginImageContext(newSize); // downside: this can't go on a background thread, I'm told
[originalImage drawInRect : CGRectMake(0, 0, newSize.width, newSize.height)];
UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext(); // get our new image
UIGraphicsEndImageContext();

// return our brand new image
return newImage;
}

Eva Schiffer

在iPhone上切片UIImage

2 个答案: