如何访问用户定义的数据类型中的数组元素？ （C）

Question

I am writing a C program to emulate background mode 7 of the SNES. I need r (red), g (green) and b (blue) values for the pixel to display at each "dot" (pixel/point) on the screen. This requires a transformation of a "tilemap" to get (The tilemap is simply a 1024 x 1024 grid of pixels that you use to decide what to place on the 256 x 224 pixel display). I need to be able to read from and write to pixels as their individual r, g and b values on the tilemap.

To quickly explain the format that I'm using there are 256 "characters" which are just 8 x 8 pixel blocks (composed of three colour bytes to represent red, green and blue). The tilemap is made up of a 128 x 128 grid of any of these characters. Once the tilemap is constructed, a transformation is preformed on the tilemap to discern the individual pixels to display on a 256 x 224 pixel screen.

To achieve this I am defining: a struct named "colour" containing three unsigned chars for the r, g and b bytes, a data type named "CHR" which is an 8 x 8 array of "colour"s, a data type named "ChrRom" which is an array of 256 "CHR"s (probably could avoid being defined but it was the only way I could think to actually have an array of arrays that I can also dereference... I think). Finally, I have a dereferenced array named "Tilemap" to (hopefully) store the memory addresses of each element in the "ChrRom" struct. I am sorry if that wasn't clear but here's the example code:

typedef struct{
    unsigned char r;
    unsigned char g;
    unsigned char b;
} colour;

typedef colour CHR[8][8];

typedef CHR ChrRom[256];

int main() {
    ChrRom *Tilemap[128][128];
    //Do other computation
    return 0;
};

So far, this will compile. However, I now want to set the colour values of a certain pixel in a character and immediately there is a problem; firstly, I cannot access the individual colours of a pixel in a "character" anymore. I only have access to the tilemap itself, secondly, I do not know how to read the colour values in the tilemap anyway. On the topic of the second problem (assume for a moment that I somehow read from a file and piped the appropriate colour values into the tilemap characters and composed the tilemap of said characters in a given order), I tried:

//Still in the function where Tilemap was declared obviously (main)
printf("%hhu\n", Tilemap[1][1].ChrRom[7].CHR[1][3].r);

GCC will not compile this. It says:

request for member 'ChrRom' in something not a structure or union

but if I remove ChrRom and CHR before the array entries, I get:

expected identifier before '[' token

Answer 1

Finally, I have a dereferenced array named "Tilemap" to (hopefully) store the memory addresses of each element in the "ChrRom" struct.

No, by defining ChrRom *Tilemap[128][128] you declare to store the memory addresses of ChrRom s (of which there exists only one). To store the memory addresses of elements in the "ChrRom" struct, you have to specify the type of those elements: CHR *Tilemap[128][128] .