我为blur函数编写了一个代码，但它返回了一个错误的输出，原因我不知道（它只是对我来说看起来很好），下面是一个例子（总是相同的）：

:( blur correctly filters middle pixel
    expected "127 140 149\n", not "126 140 149\n"
:) blur correctly filters pixel on edge
:) blur correctly filters pixel in corner
:( blur correctly filters 3x3 image
    expected "70 85 95\n80 9...", not "70 85 95\n80 9..."
:( blur correctly filters 4x4 image
    expected "70 85 95\n80 9...", not "70 85 95\n80 9..."

代码如下：

void blur(int height, int width, RGBTRIPLE image[height][width])
{
    RGBTRIPLE original[height][width];
    for (int i = 0; i < height; i++)
    {
        for (int j = 0; j < width; j++)
        {
            original[i][j] = image[i][j];
        }
    }
    for (int i = 0; i < height; i++)
    {
        for (int j = 0; j < width; j++)
        {
            if (i == 0)
            {
                if (j == 0)
                {
                    image[i][j].rgbtRed = round((original[i][j].rgbtRed + original[i + 1][j].rgbtRed + original[i][j + 1].rgbtRed + original[i + 1][j + 1].rgbtRed) / 4);
                    image[i][j].rgbtGreen = round((original[i][j].rgbtGreen + original[i + 1][j].rgbtGreen + original[i][j + 1].rgbtGreen + original[i + 1][j + 1].rgbtGreen) / 4);
                    image[i][j].rgbtBlue = round((original[i][j].rgbtBlue + original[i + 1][j].rgbtBlue + original[i][j + 1].rgbtBlue + original[i + 1][j + 1].rgbtBlue) / 4);
                }
                else if (j == width - 1)
                {
                    image[i][j].rgbtRed = round((original[i][j].rgbtRed + original[i + 1][j].rgbtRed + original[i][j - 1].rgbtRed + original[i + 1][j - 1].rgbtRed) / 4);
                    image[i][j].rgbtGreen = round((original[i][j].rgbtGreen + original[i + 1][j].rgbtGreen + original[i][j - 1].rgbtGreen + original[i + 1][j - 1].rgbtGreen) / 4);
                    image[i][j].rgbtBlue = round((original[i][j].rgbtBlue + original[i + 1][j].rgbtBlue + original[i][j - 1].rgbtBlue + original[i + 1][j - 1].rgbtBlue) / 4);
                }
                else
                {
                    image[i][j].rgbtRed = round((original[i][j].rgbtRed + original[i + 1][j].rgbtRed + original[i][j - 1].rgbtRed + original[i + 1][j - 1].rgbtRed + original[i][j + 1].rgbtRed + original[i + 1][j + 1].rgbtRed) / 6);
                    image[i][j].rgbtGreen = round((original[i][j].rgbtGreen + original[i + 1][j].rgbtGreen + original[i][j - 1].rgbtGreen + original[i + 1][j - 1].rgbtGreen + original[i][j + 1].rgbtGreen + original[i + 1][j + 1].rgbtGreen) / 6);
                    image[i][j].rgbtBlue = round((original[i][j].rgbtBlue + original[i + 1][j].rgbtBlue + original[i][j - 1].rgbtBlue + original[i + 1][j - 1].rgbtBlue + original[i][j + 1].rgbtBlue + original[i + 1][j + 1].rgbtBlue) / 6);
                }
            }
            else if (i > 0 && i < height - 1)
            {
                if (j == 0)
                {
                    image[i][j].rgbtRed = round((original[i][j].rgbtRed + original[i + 1][j].rgbtRed + original[i - 1][j].rgbtRed + original[i + 1][j + 1].rgbtRed + original[i][j + 1].rgbtRed + original[i - 1][j + 1].rgbtRed) / 6);
                    image[i][j].rgbtGreen = round((original[i][j].rgbtGreen + original[i + 1][j].rgbtGreen + original[i- 1][j].rgbtGreen + original[i + 1][j + 1].rgbtGreen + original[i][j + 1].rgbtGreen + original[i - 1][j + 1].rgbtGreen) / 6);
                    image[i][j].rgbtBlue = round((original[i][j].rgbtBlue + original[i + 1][j].rgbtBlue + original[i - 1][j].rgbtBlue + original[i + 1][j + 1].rgbtBlue + original[i][j + 1].rgbtBlue + original[i - 1][j + 1].rgbtBlue) / 6);
                }
                else if (j == width - 1)
                {
                    image[i][j].rgbtRed = round((original[i][j].rgbtRed + original[i + 1][j].rgbtRed + original[i - 1][j].rgbtRed + original[i + 1][j - 1].rgbtRed + original[i][j - 1].rgbtRed + original[i - 1][j - 1].rgbtRed) / 6);
                    image[i][j].rgbtGreen = round((original[i][j].rgbtGreen + original[i + 1][j].rgbtGreen + original[i- 1][j].rgbtGreen + original[i + 1][j - 1].rgbtGreen + original[i][j - 1].rgbtGreen + original[i - 1][j - 1].rgbtGreen) / 6);
                    image[i][j].rgbtBlue = round((original[i][j].rgbtBlue + original[i + 1][j].rgbtBlue + original[i - 1][j].rgbtBlue + original[i + 1][j - 1].rgbtBlue + original[i][j - 1].rgbtBlue + original[i - 1][j - 1].rgbtBlue) / 6);
                }
                else
                {
                    image[i][j].rgbtRed = round((original[i][j].rgbtRed + original[i][j - 1].rgbtRed + original[i][j + 1].rgbtRed + original[i + 1][j - 1].rgbtRed + original[i + 1][j + 1].rgbtRed + original[i + 1][j].rgbtRed + original[i - 1][j - 1].rgbtRed + original[i - 1][j + 1].rgbtRed + original[i - 1][j].rgbtRed) / 9);
                    image[i][j].rgbtGreen = round((original[i][j].rgbtGreen + original[i][j - 1].rgbtGreen + original[i][j + 1].rgbtGreen + original[i + 1][j - 1].rgbtGreen + original[i + 1][j + 1].rgbtGreen+ original[i + 1][j].rgbtGreen + original[i - 1][j - 1].rgbtGreen + original[i - 1][j + 1].rgbtGreen + original[i - 1][j].rgbtGreen) / 9);
                    image[i][j].rgbtBlue = round((original[i][j].rgbtBlue + original[i][j - 1].rgbtBlue + original[i][j + 1].rgbtBlue + original[i + 1][j - 1].rgbtBlue + original[i + 1][j + 1].rgbtBlue + original[i + 1][j].rgbtBlue + original[i - 1][j - 1].rgbtBlue + original[i - 1][j + 1].rgbtBlue + original[i - 1][j].rgbtBlue) / 9);
                }
            }
            else if (i == height - 1)
            {
                if (j == 0)
                {
                    image[i][j].rgbtRed = round((original[i][j].rgbtRed + original[i - 1][j].rgbtRed + original[i][j + 1].rgbtRed + original[i - 1][j + 1].rgbtRed) / 4);
                    image[i][j].rgbtGreen = round((original[i][j].rgbtGreen + original[i - 1][j].rgbtGreen + original[i][j + 1].rgbtGreen + original[i - 1][j + 1].rgbtGreen) / 4);
                    image[i][j].rgbtBlue = round((original[i][j].rgbtBlue + original[i - 1][j].rgbtBlue + original[i][j + 1].rgbtBlue + original[i - 1][j + 1].rgbtBlue) / 4);
                }
                else if (j == width - 1)
                {
                    image[i][j].rgbtRed = round((original[i][j].rgbtRed + original[i - 1][j].rgbtRed + original[i][j - 1].rgbtRed + original[i - 1][j - 1].rgbtRed) / 4);
                    image[i][j].rgbtGreen = round((original[i][j].rgbtGreen + original[i - 1][j].rgbtGreen + original[i][j - 1].rgbtGreen + original[i - 1][j - 1].rgbtGreen) / 4);
                    image[i][j].rgbtBlue = round((original[i][j].rgbtBlue + original[i - 1][j].rgbtBlue + original[i][j - 1].rgbtBlue + original[i - 1][j - 1].rgbtBlue) / 4);
                }
                else
                {
                    image[i][j].rgbtRed = round((original[i][j].rgbtRed + original[i - 1][j].rgbtRed + original[i][j - 1].rgbtRed + original[i - 1][j - 1].rgbtRed + original[i][j + 1].rgbtRed + original[i - 1][j + 1].rgbtRed) / 6);
                    image[i][j].rgbtGreen = round((original[i][j].rgbtGreen + original[i - 1][j].rgbtGreen + original[i][j - 1].rgbtGreen + original[i - 1][j - 1].rgbtGreen + original[i][j + 1].rgbtGreen + original[i - 1][j + 1].rgbtGreen) / 6);
                    image[i][j].rgbtBlue = round((original[i][j].rgbtBlue + original[i - 1][j].rgbtBlue + original[i][j - 1].rgbtBlue + original[i - 1][j - 1].rgbtBlue + original[i][j + 1].rgbtBlue + original[i - 1][j + 1].rgbtBlue) / 6);
                }
            }
        }
    }
}

我想我的解决方案要短得多

void blur(int height, int width, RGBTRIPLE image[height][width])
{
//Iterates through all the pixels

for(int i = 0; i < height; i++)
{
    for(int j = 0; j < width; j++)
    {

        //Stores average of all the pixels around the certain color

        int avgrgb[3] = {0,0,0}, n = 0;

        // Matrix “a” and “b” represent the nine pixels address around the pixel of address i and j  
 
        int a[3][3] = { {i-1, i-1, i-1}, {i, i, i}, {i+1, i+1,i+1} }, b[3][3] = { {j-1, j, j+1}, {j-1, j, j+1}, {j-1, j, j+1} };

        //Iterating through the pixels around the middle pixel           

        for(int x = 0; x < 3; x++)
        {
            for(int y = 0; y < 3; y++)
            {

                // Checking if the index contains any negative integer(negative integer represents a pixel outside the image for corner or edge pixel)

                if (a[x][y] >= 0 && a[x][y] >= 0)
                {

                    // Calculates the sum of the valid pixel colours 

                    avgrgb[0] += image[a[x][y]][b[x][y]].rgbtRed;
                    avgrgb[1] += image[a[x][y]][b[x][y]].rgbtGreen;
                    avgrgb[2] += image[a[x][y]][b[x][y]].rgbtBlue;
                    n++;
                }
            }
        }

        // Calculates the actual average    

        avgrgb[0] /= n;
        avgrgb[1] /= n;
        avgrgb[2] /= n;

        // Assigning new pixel values

        image[i][j].rgbtRed = avgrgb[0];
        image[i][j].rgbtGreen = avgrgb[1];
        image[i][j].rgbtBlue = avgrgb[2];
    }
}
return;
}

3条答案

按热度按时间

k97glaaz1#

如果结构RGBTRIPLE的成员具有整数类型，则 * 整数除法 * 发生在如下行中

image[i][j].rgbtRed = round((original[i][j].rgbtRed + original[i + 1][j].rgbtRed + original[i][j + 1].rgbtRed + original[i + 1][j + 1].rgbtRed) / 4);

并且在传递给round()函数之前将结果截断为整数。
除法器应该是浮点数，如4.0，而不是整数，如4。
如果在应用了这个修改之后，法官仍然拒绝你的答案，那应该是由于浮点数的计算错误，在这种情况下，你应该避免使用浮点数计算，而考虑如何只使用整数计算来计算想要的值。

赞(0）回复(0）举报 2022-12-02

ltqd579y2#

qacovj5a3#

MikeCAT的答案当然是正确的。作为他建议的替代方案，你可以在整数除法之前加上一半的除数来避免浮点数的转换。

image[i][j].rgbtRed = (original[i][j].rgbtRed + … + original[i+1][j+1].rgbtRed + 2) / 4;
…
image[i][j].rgbtRed = (original[i][j].rgbtRed + … + original[i-1][j  ].rgbtRed + 4) / 9;

CS50 pset4滤镜模糊功能

3条答案

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