问题描述
我在尝试解决 CS50 中的边缘检测问题时遇到了问题。
下面是我的代码:
// Detect edges
void edges(int height,int width,RGBTRIPLE image[height][width])
{
// Ask for some temparory memories for store blur pixels
RGBTRIPLE temp[height][width];
// Consider every condition you may encounter with pixels
int GxR,GyR,GxG,GyG,GxB,GyB;
// Initialize Gx and Gy metrix
int Gx[3][3] = {{-1,1},{-2,2},{-1,1}};
int Gy[3][3] = {{-1,-2,-1},{0,0},{1,2,1}};
for (int i = 0; i < height; i++)
{
for (int j = 0; j < width; j++)
{
GxR = GyR = GxG = GyG = GxB = GyB= 0;
// Loop over 3x3 pixels
for (int h = -1; h < 2; h++)
{
for (int w = -1; w < 2; w++)
{
// Check if this pixel is outside the image
if (i + h < 0 || i + h > height - 1)
{
continue;
}
if (j + w < 0 || j + w > width - 1)
{
continue;
}
// sum each channel value
// X
GxR += image[i + h][j + w].rgbtRed * Gx[h + 1][w + 1];
GxG += image[i + h][j + w].rgbtGreen * Gx[h + 1][w + 1];
GxB += image[i + h][j + w].rgbtBlue * Gx[h + 1][w + 1];
// Y
GyR += image[i + h][j + w].rgbtRed * Gy[h + 1][w + 1];
GyG += image[i + h][j + w].rgbtGreen * Gy[h + 1][w + 1];
GyB += image[i + h][j + w].rgbtBlue * Gy[h + 1][w + 1];
}
}
// Calculate every Gx and Gy value and store in temp
temp[i][j].rgbtRed = round(sqrt((GxR * GxR + GyR * GyR)));
temp[i][j].rgbtGreen = round(sqrt((GxG * GxG + GyG * GyG)));
temp[i][j].rgbtBlue = round(sqrt((GxB * GxB + GyB * GyB)));
// Capped color value at 255
if (temp[i][j].rgbtRed > 255)
{
temp[i][j].rgbtRed = 255;
}
if (temp[i][j].rgbtGreen > 255)
{
temp[i][j].rgbtGreen = 255;
}
if (temp[i][j].rgbtBlue > 255)
{
temp[i][j].rgbtBlue = 255;
}
}
}
// Ready to iterate whole image from temp to image[i][j]
for (int i = 0; i < height; i++)
{
for (int j = 0; j < width; j++)
{
image[i][j] = temp[i][j];
}
}
return;
}
当我运行 check50 时,结果显示像素的红色和绿色值是正确的,但只有蓝色是错误的。结果如下:
:( edges correctly filters pixel on edge
expected "213 228 255\n",not "213 228 140\n"
:( edges correctly filters pixel in corner
expected "76 117 255\n",not "76 117 66\n"
:( edges correctly filters 3x3 image
expected "76 117 255\n21...",not "76 117 66\n213..."
:( edges correctly filters 4x4 image
expected "76 117 255\n21...",not "76 117 66\n213..."
有人能告诉我我的代码有什么问题吗?
我已经尽力调试了,但还是找不到哪里出了问题...
解决方法
您的 edges
函数几乎是正确的。你只是错过了
// Calculate every Gx and Gy value and store in temp
temp[i][j].rgbtRed = round(sqrt((GxR * GxR + GyR * GyR)));
temp[i][j].rgbtGreen = round(sqrt((GxG * GxG + GyG * GyG)));
temp[i][j].rgbtBlue = round(sqrt((GxB * GxB + GyB * GyB)));
成员 rgbtRed
、rgbtGreen
和 rgbtBlue
只有 8 位,并且将浮点类型值从 256 分配给它们的行为是未定义的;以下用于限制值的代码不起作用。因此,在分配 RGB 值之前对其进行上限:
temp[i][j].rgbtRed = fmin(round(sqrt(GxR * GxR + GyR * GyR)),255);
temp[i][j].rgbtGreen = fmin(round(sqrt(GxG * GxG + GyG * GyG)),255);
temp[i][j].rgbtBlue = fmin(round(sqrt(GxB * GxB + GyB * GyB)),255);