Question

我为模糊函数编写了一个代码，但由于我不知道的原因返回了错误的输出（对我来说它看起来很好），这是一个示例（始终相同）：

:( 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..."

代码在这里：

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);
                }
            }
        }
    }
}

Answer 1

如果结构 RGBTRIPLE 的成员具有整数类型，整数除法发生在像

这样的行中

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);

并且结果在传递给 round() 函数之前被截断为整数。

分隔符应该是像 4.0 这样的浮点数，而不是像 4 这样的整数。

如果应用此更改后法官仍然拒绝您的答案，则应该是由于浮点数的计算错误。在这种情况下，您应该避免使用浮点数计算，而应考虑如何仅使用整数计算来计算所需的值。

Answer 2

MikeCAT 的回答肯定是正确的。作为他建议的替代方案，您可以通过在整数除法之前添加除数的一半来避免与浮点之间的转换，例如。 g.

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

2 个答案: