C, BMP processing...no clue :/
I am supposed to read in a .bmp file and then alter it based on command line arguements.
Examples:
-fromrow x, where x specifies the bottommost row to process -torow x, where x specifies the topmost row to process -fromcol x, where x specifies the leftmost column to process -tocol x, where x specifies the rightmost column to process -op x, where x is one of the following -- 1= threshold the image(any pixel value in the specifies range over 127 is changed t0 255, and pixel values 127 or less is changed to 0) -- 2= negative (any pixel value p in the specified range is changed to 255-p)I have been given this code as am example of reading a .bmp file:
#include <stdio.h>
#include <stdlib.h>
int main() {
FILE *fp= fopen("sample.bmp", "r+");
if (fp == NULL){
printf("Error");
}
int temp=0;
//Go to Byte 22
fseek(fp,22,SEEK_SET);
//Read byte 22 into an integer variable
fread(&temp, size开发者_Go百科of(int), 1, fp);
printf("Number of Rows: %d\n", temp);
fseek(fp,18,SEEK_SET);
fread(&temp, sizeof(int), 1, fp);
printf("Number of Columns: %d\n", temp);
fseek(fp,10,SEEK_SET);
fread(&temp, sizeof(int), 1, fp);
printf("Start of Pixels: %d\n", temp);
fclose (fp);
}
What is "Start of Pixels"? I suppose I somehow loope through the bytes of the image and copy them into a 2D array...but I don't know the suntax for accessing the files bytes?
I don't even know where to start in terms of altering an image... :/ I'm at a loss. ANY help/advice/linfo/links would be greatly appreciated.
Thank you in advance.
You'll want to start by reading in a BITMAPFILEHEADER
, then a BITMAPINFO
(which contains a BITMAPINFOHEADER
). These will give you the information necessary to find and interpret the pixels.
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