I have created with GIMP a C-Source image dump like the following:

/* GIMP RGBA C-Source image dump (example.c) */

static const struct {
  guint      width;
  guint      height;
  guint      bytes_per_pixel; /* 2:RGB16, 3:RGB, 4:RGBA */ 
  guint8     pixel_data[304 * 98 * 2   1];
} example= {
  304, 98, 2,
  "\206\061\206\061..... }

Is there a way to read this in GIMP again in order to get back the original image? because it doesn't seem possible. Or does it exist a tool that can do this back-conversion?

EDITED Following some suggestion I tried to write a simple C programme to make the reverse coversion ending up with something very similar to another code found on internet but both dont work:

#include <stdlib.h> #include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include "imgs_press.h" #include<stdio.h> #include <unistd.h> #include <fcntl.h>

using namespace std;

int main(int argc, char** argv) {
    int fd;
    char *name = "orignal_img.pnm";
    fd = open(name, O_WRONLY | O_CREAT, 0644);
    if (fd == -1) {
        perror("open failed");
        exit(1);
    }

    if (dup2(fd, 1) == -1) {
        perror("dup2 failed"); 
        exit(1);
    }

    // file descriptor 1, i.e. stdout, now points to the file
    // "helloworld" which is open for writing
    // You can now use printf which writes specifically to stdout


    printf("P2\n");
    printf("%d %d\n", press_high.width, press_high.height);
    for(int x=0; x<press_high.width * press_high.height * 2; x  ) {
        printf("%d ", press_high.pixel_data[x]);
    }

}

As suggested by n-1-8e9-wheres-my-share-m, maybe I need to manipulate the pixels usign the correct decode, but I have no idea how to do that, does anybody have other suggestions?

The image I got is indeed distorted:

CodePudding user response：

Updated Answer

If you want to decode the RGB565 and write a NetPBM format PNM file without using ImageMagick, you can do this:

#include <stdint.h>   /* for uint8_t */
#include <stdio.h>    /* for printf */

/* tell compiler what those GIMP types are */
typedef int guint;
typedef uint8_t guint8;

#include <YOURGIMPIMAGE>

int main(){

   int w = gimp_image.width;
   int h = gimp_image.height;
   int i;
   uint16_t*  RGB565p = (uint16_t*)&(gimp_image.pixel_data);

   /* Print P3 PNM header on stdout */
   printf("P3\n%d %d\n255\n",w, h);

   /* Print RGB pixels, ASCII, one RGB pixel per line */
   for(i=0;i<w*h;i  ){
      uint16_t RGB565 = *RGB565p  ;
      uint8_t r = (RGB565 & 0xf800) >> 8;
      uint8_t g = (RGB565 & 0x07e0) >> 3;
      uint8_t b = (RGB565 & 0x001f) << 3;
      printf("%d %d %d\n", r, g ,b);
   }
}

Compile with:

clang example.c

And run with:

./a.out > result.pnm

I have not tested it too extensively beyond your sample image, so you may want to make a test image with some reds, greens, blues and shades of grey to ensure that all my bit-twiddling is correct.

Original Answer

The easiest way to get your image back would be... to let ImageMagick do it.

So, take your C file and add a main() to it that simply writes the 304x98x2 bytes starting at &(example.pixel_data) to stdout:

Compile it with something like:

clang example.c -o program    # or with GCC
gcc example.c -o program

Then run it, writing to a file for ImageMagick with:

./program > image.bin

And tell ImageMagick its size, type and where it is and what you want as a result:

magick -size 304x98 RGB565:image.bin result.png

I did a quick, not-too-thorough test of the following code and it worked fine for an image I generated with GIMP. Note it doesn't handle alpha/transparency but that could be added if necessary. Save it as program.c:

#include <unistd.h>   /* for write() */
#include <stdint.h>   /* for uint8_t */

/* tell compiler what those GIMP types are */
typedef int guint;
typedef uint8_t guint8;

<PASTE YOUR GIMP FILE HERE>

int main(){

   /* Work out how many bytes to write */
   int nbytes = example.width * example.height * 2;

   /* Write on stdout for redirection to a file - may need to reopen in binary mode if on Windows */
   write(1, &(example.pixel_data), nbytes);
}

If I run this with the file you provided via Google Drive I get: