How to store 2d array into a new array...(beaglebone black)

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C

Linux

I'm working with bmp images, which I'm passing a a 2d array by reference to a function that opens the bmp and stores it using a struct. When the function exits, I have a reference to an address. I can add it to a new array to store the opened bmp, but as it is a reference all locations of the new array have the same reference.

see https://www.codeproject.com/Questions/5248639/Why-is-my-array-index-values-all-the-same as a reference to my original problem.

So I need to de-reference and only insert the 2d array values. How do I go about doing this.

typedef struct pixel {
	uint8_t r;
	uint8_t g;
	uint8_t b;

} pixel;

//image_names = name of all images which have been sorted
//num_images = total number of images
//IMG_Y = 360
//IMG_X = 640

pixel** img;
struct pixel** images[num_images];

// Allocate image structure which will be used to load images
img = (pixel**)malloc (IMG_Y * sizeof (pixel*));
for (i = 0; i < IMG_Y; i++) 
{
		img[i] = (pixel*)malloc (IMG_X * sizeof (pixel));
}

for (i = 0; i < num_images; i++)
{
	// Open image and ensure it's successful. 
	if (open_bmp (*(image_names + i), img) == EXIT_FAILURE) 
    {
		return EXIT_FAILURE;
	}

	images[i] = img;
	}
}

int open_bmp (char * file_name, pixel** img) {
	// Variable declarations
	long offset = 0;
	unsigned char buff[100];
	int x = 0, y = 0;
	FILE *f = fopen (file_name, "rb"); // open file in binary mode

	// Read pixel data
	fseek (f, offset, SEEK_SET); // go to beginning of pixel data
	while ((fread (&buff, 3, 1, f) >= 1) && y < IMG_Y) // while not EOF (or done with image), read next pixel
	{
		img[y][x].r = buff[2];
		img[y][x].g = buff[1];
		img[y][x].b = buff[0];

		x++; // read next column
		if (x >= IMG_X) { // finished reading row, go to next row
			y++;
			x = 0;
		}
	}

	if (PRINTBMPDATA) {
		for (y = 0; y < IMG_Y; y++) {
			for (x = 0; x < IMG_X; x++) {
				printf ("%02x%02x%02x ", img[y][x].b, img[y][x].g, img[y][x].r);
			}
			printf ("\n");
		}
		printf ("\n");
	}

	// Close image file now that we have copied it to the img structure
	if (fclose (f)) {
		printf ("Unable to close image file\n");
		return EXIT_FAILURE;
	}

	return EXIT_SUCCESS;
}

What I have tried:

What I have attempted to do was de-reference. Which only inserted a single value of 0.

images[i] = **img

the result was just a 1D array

Next I thought I should attempt to pass a 3D array, modify the open_bmp() and just do the same thing I'm doing now, but when passed to open_bmp() fill levels 2 and 3. here are the changes I made.

pixel*** img;

	// Allocate image structure which will be used to load images
	img = (pixel***)malloc (num_images * sizeof (pixel**));
	for(i = 0; i < num_images; i++)
	{

		img[i] = (pixel**)malloc (IMG_Y * sizeof (pixel*));
		for (k = 0; k < IMG_Y; i++)
			img[i][k] = (pixel*)malloc (IMG_X * sizeof (pixel));
	}

for (i = 0; i < num_images; i++)
	{
	// Open image and ensure it's successful. Inefficent to load file everytime but fine at BeagleBone's low effective video framerates
		if (open_bmp (*(image_names + i), img, i) == EXIT_FAILURE) {
			return EXIT_FAILURE;
		}
	}

int open_bmp (char * file_name, pixel*** img, int idx) {

	printf ("Index: %d\n", idx);
	// Variable declarations
	long offset = 0;
	unsigned char buff[100];
	int x = 0, y = 0;
	FILE *f = fopen (file_name, "rb"); // open file in binary mode

	// Read pixel data
	fseek (f, offset, SEEK_SET); // go to beginning of pixel data
	while ((fread (&buff, 3, 1, f) >= 1) && y < IMG_Y) // while not EOF (or done with image), read next pixel
	{
		img[idx][y][x].r = buff[2];
		img[idx][y][x].g = buff[1];
		img[idx][y][x].b = buff[0];

		x++; // read next column
		if (x >= IMG_X) { // finished reading row, go to next row
			y++;
			x = 0;
		}
	}

	if (PRINTBMPDATA) {
		for (y = 0; y < IMG_Y; y++) {
			for (x = 0; x < IMG_X; x++) {
				printf ("%02x%02x%02x ", img[idx][y][x].b, img[idx][y][x].g, img[idx][y][x].r);
			}
			printf ("\n");
		}
		printf ("\n");
	}

	// Close image file now that we have copied it to the img structure
	if (fclose (f)) {
		printf ("Unable to close image file\n");
		return EXIT_FAILURE;
	}

	return EXIT_SUCCESS;
}

while I wrote a test case and it works fine, I've found a lot of references stating 3d+ arrays are a bad idea in this manner. The other issue, is the actual program doesn't execute.