#include <stdio.h>

float hmap[2048][2048];
float hmin, hmax;
unsigned char res1[1024][1024];
unsigned char res2[512][512];
unsigned char res3[256][256];


void MakeMultires() {
	int i, j, r;
	float avg;
	// **************** find hmin and hmax ************
	hmin = hmax = hmap[0][0];
	for (i=0;i<2048;i++) {
		for (j=0;j<2048;j++) {
			if (hmap[i][j]>hmax) hmax = hmap[i][j];
			if (hmap[i][j]<hmin) hmin = hmap[i][j];
		}
	}
	// **************** set res1 **********************
	for (i=0;i<1024;i++) {
		for (j=0;j<1024;j++) {
			avg = hmap[i*2][j*2];
			avg += hmap[i*2+1][j*2];
			avg += hmap[i*2+1][j*2+1];
			avg += hmap[i*2][j*2+1];
			avg /= 4.0;
			avg = 255.0 * (avg - hmin) / (hmax - hmin);
			res1[i][j] = (unsigned char) avg;
		}
	}
	// **************** set res2 **********************
	for (i=0;i<512;i++) {
		for (j=0;j<512;j++) {
			r = res1[i*2][j*2];
			r += res1[i*2+1][j*2];
			r += res1[i*2+1][j*2+1];
			r += res1[i*2][j*2+1];
			r /= 4;
			res2[i][j] = r;
		}
	}
	// **************** set res3 **********************
	for (i=0;i<256;i++) {
		for (j=0;j<256;j++) {
			r = res2[i*2][j*2];
			r += res2[i*2+1][j*2];
			r += res2[i*2+1][j*2+1];
			r += res2[i*2][j*2+1];
			r /= 4;
			res3[i][j] = r;
		}
	}
}

void ReadBinary(char *fname) {
	FILE *fptr;
	fptr = fopen(fname,"rb");
	fread(hmap,2048*2048,sizeof(float),fptr);
	fclose(fptr);
}

void WriteBinary(char *fname) {
	FILE *fptr;
	fptr = fopen(fname,"wb");
	fwrite(hmap,2048*2048,sizeof(float),fptr);
	fclose(fptr);
}

void WriteText(char *fname) {
	int i, j;
	FILE *fptr;
	fptr = fopen(fname,"wt");
	for (i=0;i<256;i++) {
		for (j=0;j<256;j++) {
			fprintf(fptr, "%d ", (int)res3[i][j]);
		}
		fprintf(fptr, "\n");
	}
	fclose(fptr);
}

int main() {
	// read hmap from file
	ReadBinary("highres.hmp");
	// make multires
	MakeMultires();
	// write res3 to file
	WriteText("lowres.txt");
	return 0;
}