Elie at 18:10, 7 August 2022

2022-08-07T18:10:11Z

← Older revision		Revision as of 14:10, 7 August 2022
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			Generates the image [[:File:borders-black-on-white.png\|borders-black-on-white.png]] from raw data [[:File:countries.data-int16-8640x4320\|countries.data-int16-8640x4320]]

	<syntaxhighlight lang="c">		<syntaxhighlight lang="c">
	#define WIDTH 8640		#define WIDTH 8640

Elie: Created page with " #define WIDTH 8640 #define HEIGHT 4320 #define IN_FILE "data/countries.data-int16-8640x4320" #define OUT_FILE "data/borders-black-on-white.png" #include #define STB_IMAGE_WRITE_IMPLEMENTATION #include "stb_image_write.h" int main() { short in = malloc(WIDTHHEIGHTsizeof(short)); unsigned char out = malloc(WIDTHHEIGHTsizeof(unsigned char)); if (!in || !out) { printf("Not enough memory\n"); free(in); free(out);..."

2022-08-07T08:11:53Z

Created page with "<syntaxhighlight lang="c"> #define WIDTH 8640 #define HEIGHT 4320 #define IN_FILE "data/countries.data-int16-8640x4320" #define OUT_FILE "data/borders-black-on-white.png" #include <stdio.h> #define STB_IMAGE_WRITE_IMPLEMENTATION #include "stb_image_write.h" int main() { short *in = malloc(WIDTH*HEIGHT*sizeof(short)); unsigned char *out = malloc(WIDTH*HEIGHT*sizeof(unsigned char)); if (!in || !out) { printf("Not enough memory\n"); free(in); free(out);..."

New page

<syntaxhighlight lang="c">
#define WIDTH 8640
#define HEIGHT 4320
#define IN_FILE "data/countries.data-int16-8640x4320"
#define OUT_FILE "data/borders-black-on-white.png"

#include <stdio.h>
#define STB_IMAGE_WRITE_IMPLEMENTATION
#include "stb_image_write.h"

int main() {
short *in = malloc(WIDTH*HEIGHT*sizeof(short));
unsigned char *out = malloc(WIDTH*HEIGHT*sizeof(unsigned char));
if (!in || !out) {
printf("Not enough memory\n");
free(in); free(out);
return 1;
}

// load data
printf("Reading %s\n", IN_FILE);
FILE *f = fopen(IN_FILE,"r"); if (!f) { perror(IN_FILE); return 2; }
if (!fread(in, sizeof(in[0]), WIDTH*HEIGHT, f)) printf("Input file is incomplete. Output will probably be garbage lol\n");
fclose(f);

// simplest edge-detection algorithm i can think of lol
printf("Detecting edges\n");
int i; for (i=0; i<WIDTH; i++) out[i]=255;
for (; i<WIDTH*(HEIGHT-1); i++) {
if (in[i] != in[i+1]
|| in[i] != in[i-1]
|| in[i] != in[i-WIDTH]
|| in[i] != in[i+WIDTH]) out[i]=0;
else out[i]=255;
}
for (; i<WIDTH*HEIGHT; i++) out[i]=255; // top and bottom rows of pixels are ignored, for simplicity sake. The dataset doesn't have edges there anyway.

// write file and done
int r=0;
printf("Writing %s\n", OUT_FILE);
free(in);
if (!stbi_write_png(OUT_FILE, WIDTH, HEIGHT, 1, out, WIDTH)) { perror(OUT_FILE); r=3; }
free(out);
return r;
}
</syntaxhighlight>

Code:borders-black-on-white.c - Revision history

Elie at 18:10, 7 August 2022