[greggman3]

I don't consider ASCII simple because it needs to be parsed (more than a binary format).

As sample example, a binary format could be as simple as

    struct Header {
      uint32 width;
      uint32 height;
    }

    struct Image {
      Header header;
      uint8* data;
    }

    Image* readIMG(const char* filename) {
      int fd = open(filename, ...)
      Image* image = new Image();
      read(fd, &image->header, sizeof(image->header));
      size_t size = image->header.width * image->header.height * 4;
      image->data = malloc(size);
      read(fd, image->data, size);
      close(fd);
      return image;
    }

Yea I know, that's not a complete example, endian issues, error checking.

Reading a PPM file is only simple if you already have something to read buffered strings and parse numbers etc... And it's slow and large, especially for todays files.