java - 二维数组子采样 - java

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这个问题已经有答案了:

Compare two arrays of primitives in Java? (3 个回答)

已关闭 6 年前。

我正在尝试对 8x8 二维数组列表进行子采样。更准确地说，我想从 8x8 转换为 4x4，方法是逐一取出 2x2 block ，并将 2x2 的算术平均值保存在 4x4 中的正确位置。执行此操作后，输出将是 4x4 二维数组的列表。以下两个方法正在处理这个问题

public static long[][] subSample420(long[][] originalBlocks){
    long[][] downsampledBlocks = new long[4][4];
    long[] mediePixel = new long[16];
    int nr = 0;
    for (int i = 0; i < 8; i += 2){
        for (int j = 0; j < 8; j += 2){
            mediePixel[nr] = Math.round((double)(originalBlocks[i][j] + originalBlocks[i][j+1] + originalBlocks[i+1][j] + originalBlocks[i+1][j+1]) / 4);
            nr++;
        }
    }
    nr = 0;
    for (int i = 0; i < 4; i++){
        for (int j = 0; j < 4; j++){
            downsampledBlocks[i][j] = mediePixel[nr];
            nr++;
        }
    }
    return downsampledBlocks;
}


public static List<long[][]> subSampleBlocks(List<long[][]> originalBlockList){
    List<long[][]> downsampledBlockList = new ArrayList<long[][]>();
    for (long[][] anOriginalBlockList : originalBlockList) {
        downsampledBlockList.add(subSample420(anOriginalBlockList));
    }
    return downsampledBlockList;
}

现在，完成子采样后，我必须将 4x4 2d 数组的大小调整回其初始大小，这意味着通过替换4x4 与相同值的 2x2 block 。执行此操作的两种方法如下:

public static long[][] resizeSubsampledBlocks(long[][] subBlocks){
    long[][] resizedBlocks = new long[8][8];
    int nr = 0;
    long[] pixel = new long[16];
    for (int i = 0; i < 4; i++){
        for (int j = 0; j < 4; j++){
            pixel[nr] = subBlocks[i][j];
            nr++;
        }
    }
    nr = 0;
    for (int i = 0; i < 8; i += 2){
        for (int j = 0; j < 8; j += 2){
            resizedBlocks[i][j] = pixel[nr];
            resizedBlocks[i][j+1] = pixel[nr];
            resizedBlocks[i+1][j] = pixel[nr];
            resizedBlocks[i+1][j+1] = pixel[nr];
            nr++;
        }
    }
    return resizedBlocks;
}


public static List<long[][]> reziseSubsampledBlockList(List<long[][]> subBlocks){
    List<long[][]> rezisedBlocks = new ArrayList<long[][]>();
    for (long[][] subBlock : subBlocks) {
        rezisedBlocks.add(resizeSubsampledBlocks(subBlock));
    }
    return rezisedBlocks;
}

但是当我尝试使用以下方法测试所有这些时:

private static void testOrderSub(int nr){
    List<long[][]> testList = new ArrayList<long[][]>();
    for (int i = 0; i < nr; i++){
        long[][] matrix = {
                {i,     i,     i+1,   i+1,   i+2,   i+2,   i+3,   i+3},
                {i,     i,     i+1,   i+1,   i+2,   i+2,   i+3,   i+3},
                {i+4,   i+4,   i+5,   i+5,   i+6,   i+6,   i+7,   i+7},
                {i+4,   i+4,   i+5,   i+5,   i+6,   i+6,   i+7,   i+7},
                {i+8,   i+8,   i+9,   i+9,   i+10,  i+10,  i+11,  i+11},
                {i+8,   i+8,   i+9,   i+9,   i+10,  i+10,  i+11,  i+11},
                {i+12,  i+12,  i+13,  i+13,  i+14,  i+14,  i+15,  i+15},
                {i+12,  i+12,  i+13,  i+13,  i+14,  i+14,  i+15,  i+15}};
        testList.add(matrix);
    }

    List<long[][]> subTest = FirstLevelEncoder.subSampleBlocks(testList);
    List<long[][]> sizeTest = FirstLevelDecoder.reziseSubsampledBlockList(subTest);
    for (int i = 0; i < nr; i++) {
        if (!(Arrays.equals(testList.get(i), sizeTest.get(i)))){
            System.out.println("false");
        }
    }
}

sizeTest.equals(testList)返回 false，即使通过在调试器中查看它们似乎具有相同的值。我尝试使用这些方法来处理图像，但输出也很困惑。难道我做错了什么？为什么列表不相等？

Answer 1

对于 Java 数组 equals() 的测试类似于 array1==array2。它检查是否是同一个对象。它不检查是否具有相同的内容。

你必须使用

Arrays.equals(array1, array2);

这是关于 Java 数组的另一个解释:equals vs Arrays.equals in Java