C++: .bmp to byte array in a file

Question

Yes i have been through the other questions that are related to this, but i found them not much help. They were some help but i am still a bit confused. So here what what i need to do: We have a 132x65 screen. I have a 132x65 .bmp. I want to go through the .bmp and separate it into little 1x8 columns to get the binary of that 32-bit column. Then do that 132 times across, and do that 9 times down. Anything that is not white should be counted as a bit. example: If the top left pixel of the picture is any color that is not white and the 7 pixels below that are white then that would be the first element of the array, the hex of that number, so the array would look like this: array [] = { 0x01 } and then it would continue to fill through those 132 columns and then do it again for 9 "sections" of rows. And the file result would be ONLY that array in a separate file. I understand the header format for this, i have read the wiki article on .bmp file formats, my main problem is i don't really…

Accepted Answer

If you want to read a known format BMP and don't care about how it's done (ie, internal-only thing) you can just take the BMP, ignore the header and use it as a pixel array. It is stored line by line starting at the bottom left. There are some detail snags for how it's packed but in my experience if you take a 32bpp image it can be completely ignored.

As a really simple example:

```
unsigned int *buffer;
void readfile() {
    FILE *f = fopen("file.bmp", "rb");
    buffer = new unsigned int[132*65];
    fseek(f, 54);
    fread(buffer, 132*65*4, 1, f);
    fclose(f);
}

unsigned int getpixel(int x, int y) {
    //assuming your x/y starts from top left, like I usually do
    return buffer[(64 - y) * 132 + x];
}
```

C++: .bmp to byte array in a file

Solution

Problem