CODEWITHSUNDEEP
cmultidimensional-arrayppm
Christina F.
Christina F.

Reputation: 21

How to read a PPM file into standard input

I'm having trouble figuring out how to read in a ppm file into the standard input, storing the pixels in a 2- dimensional array of new_pix in C. I don't really know How to get it started. Thanks in advance!

Upvotes: 0

Views: 568

Answers (1)

Yash Gupta
Yash Gupta

Reputation: 588

I assume you can get the dimensions of the image from the file (call them W and H). If not, read about the format from wikipedia

Now, you need to allocate memory for the 2d-array you want to make. You will need a char **buf (assuming 8-bit grayscale. You can use long or long long for 32/64 bit images.

Next allocate the space for pointers where you will store the rows of the image. 

buf=(char**)malloc(sizeof(char*)*H);

Next, you need to allocate space for each row and read it from stdin (you can use scanf in a loop).

for(int y=0;y<H;y++){
  buf[y]=(char*)malloc(sizeof(char)*W);
  for(int x=0;x<W;x++)
    scanf("%d",&buff[y][x]);
}

And you are done! Note that you will have to do checks on malloc return value and limit W and H to sane values if you plan to distribute the code.

Upvotes: 1

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