Horizontal Transformation of Array (2D)

问题

It's a simple matter of flipping an image horizontally and/or vertically. The premise is that given a 2D integer array that was created from importing a picture, I must create a method with a int[][] param and horizontally flip it before returning void.

The syntax is below:

public static void horizontalFlip(int[][] imgArray)
    {
        int temp;
        for (int i = 0; i < imgArray.length; i++)
        {
            for (int j = 0; j < imgArray[i].length / 2; j++)
            {
                temp = imgArray[i][j];
                imgArray[i][j] = imgArray[imgArray.length - 1 - i][j];
                imgArray[imgArray.length - 1 - i][j] = temp;
            }
        }
    }

I use imgArray as the array param and use temp as a placeholder while the loop swaps pixels, or rather, that was the intention. Currently the window does nothing after prompting the flip. Can somebody help me find the problem with the logic or syntax?

Thanks in advance, please specify any details I should provide P.S. I can confirm the unreferenced supplied code is functional and tested.

回答1:

It is happening because you are using i instead of j. But i will not stop after halfway, but it is continued and re-swap the array.
Here is a correct code :

for (int i = 0; i < imgArray.length; i++) {
    for (int j = 0; j < imgArray[i].length / 2; j++) {
        temp = imgArray[i][j];
        imgArray[i][j] = imgArray[i][imgArray.length - 1 - j];
        imgArray[i][imgArray.length - 1 -j] = temp;
    }
}

Or if you want to swap columns, not rows :

for (int i = 0; i < imgArray.length / 2; i++) {
    for (int j = 0; j < imgArray[i].length; j++) {
        temp = imgArray[i][j];
        imgArray[i][j] = imgArray[imgArray.length - 1 - i][j];
        imgArray[imgArray.length - 1 -i][j] = temp;
    }
}

回答2:

This will correctly flip the image horizontally:

public static void horizontalFlip(int[][] imgArray)
{
    int temp;
    for (int i = 0; i < imgArray.length; i++) {
        for (int j = 0; j < imgArray[i].length/2; j++) {
        temp = imgArray[i][j];
        imgArray[i][j] = imgArray[i][imgArray[i].length - 1 - j];
        imgArray[i][imgArray[i].length - 1 - j] = temp;
        }
    }
}

来源：https://stackoverflow.com/questions/28130828/horizontal-transformation-of-array-2d