图像处理 - 如何在 C 语言中将一维数组映射到二维数组

Question

我正在尝试将图像的RGB像素分别映射到R，G，B的2D数组。当读取图像时，像素以{r1，g1，b1，r2，g2，b2...}的形式存储在一维数组中。数组的长度为 3*height*width 。2D 数组的宽度 X 高度尺寸

for(i = 0; i < length; i++) { // length = 3*height*width
    image[i][2] = getc(f); // blue pixel
    image[i][1] = getc(f); // green pixel
    image[i][0] = getc(f); // red pixel
    img[count] = (unsigned char)image[i][0];
    count += 1;
    img[count] = (unsigned char)image[i][1];
    count += 1;
    img[count] = (unsigned char)image[i][2];
    count += 1;
    printf("pixel %d : [%d,%d,%d]n", i+1, image[i][0], image[i][1], image[i][2]);
}

RGB 值以 img[] 为单位。二维数组为红色[][]、绿色[][]和蓝色[][]。

请帮忙！

Answer 1

据我了解，您正在尝试重建色域。 只需反转您的功能：

unsigned char * imgptr = img;
for( int y = 0; y < height; y++ ) {
    for( int x = 0; x < width; x++ ) {
        red[y][x] = *imgptr++;
        green[y][x] = *imgptr++;
        blue[y][x] = *imgptr++;
    }
}

要动态创建数组，请执行以下操作：

unsigned char** CreateColourPlane( int width, int height )
{
    int i;
    unsigned char ** rows;
    const size_t indexSize = height * sizeof(unsigned char*);
    const size_t dataSize = width * height * sizeof(unsigned char);
    // Allocate memory for row index and data segment.  Note, if using C compiler
    // do not cast the return value from malloc.
    rows = (unsigned char**) malloc( indexSize + dataSize );
    if( rows == NULL ) return NULL;
    // Index rows.  Data segment begins after row index array.
    rows[0] = (unsigned char*)rows + height;
    for( i = 1; i < height; i++ ) {
        rows[i] = rows[i-1] + width;
    }
    return rows;
}

然后：

unsigned char ** red = CreateColourPlane( width, height );
unsigned char ** green = CreateColourPlane( width, height );
unsigned char ** blue = CreateColourPlane( width, height );

您可以轻松释放它们，但是如果您包装了分配器函数，则包装免费函数总是值得的：

void DeleteColourPlane( unsigned char** p )
{
    free(p);
}