Question

我正在尝试对8x8 2d阵列列表进行子采样。更确切地说，从8x8开始，我想通过逐个采用2x2块将2x2的算术平均值保存在4x4的正确位置，从而转换为4x4。执行此操作后，输出将是4x4 2d阵列的列表。以下两种方法正在处理这个

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;
}

现在我完成子采样之后，我必须将4x4 2d阵列的大小调整回原始大小，这意味着通过替换单个值将4x4 2d阵列列表转换回8x8 2d阵列列表从4x4开始，具有相同值的2x2块。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，即使通过查看调试器它们似乎具有相同的值。我尝试使用这些方法处理图像，输出也搞砸了。难道我做错了什么？为什么列表不相等？

Answer 1

对于Java-Array，equals（）的测试类似于array1 == array2。它检查它是否是同一个对象。它不会检查它是否具有相同的内容。

你必须使用

Arrays.equals(array1, array2);

以下是关于Java-Arrays的另一种解释：equals vs Arrays.equals in Java

2d数组子采样 - java

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