first working version

challenge248.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#define PI 3.14159265

// https://www.reddit.com/r/dailyprogrammer/comments/3zfajl/20160104_challenge_248_easy_draw_me_like_one_of/

struct rgb_t {
	unsigned char r;
	unsigned char g;
	unsigned char b;
};

typedef struct rgb_t rgb_t;

void printGraph(int outputWidth, int outputHeight, rgb_t *pixels){
	int x, y;
	for(y = 0; y<outputHeight; y+=1){
		for(x = 0; x<outputWidth; x+=1){
			rgb_t *pixel = &pixels[y*outputWidth + x];
			printf("%i %i %i  ", pixel->r, pixel->g, pixel->b);
			if(x != outputWidth-1) printf(" ");
		}
		printf("\n");
	}
}

int main(int argc, char **argv){
	
	if(argc == 1){
		printf("Requires input file.\n");
		return 1;
	}
	
	rgb_t BACKGROUND_COLOR = {0,0,0};
	
	char *filename = argv[1];
	// printf("Loading file: %s\n", filename);
	
	// Read the input file.
	FILE *fd = fopen(filename, "rb");
	fseek(fd, 0, SEEK_END);
	int filesize = ftell(fd);
	rewind(fd);
	
	char *buffer = (char*) malloc(filesize+1);
	fread(buffer, sizeof(char), filesize, fd);
	buffer[filesize] = '\0';
	
	fclose(fd);
	
	// Print our input.
	// printf("INPUT:\n%s\n", buffer);
	
	// Replace new lines and spaces with null bytes.
	int x, count = 0;
	for(x = 0; x<filesize; x+=1){
		if(buffer[x] == '\n' || buffer[x] == ' '){
			buffer[x] = '\0';
			count += 1;
		}
	}
	
	// Convert to a C-string array for easy access!
	char *elements[count];
	elements[0] = buffer;
	int ncount=1;
	for(x = 0; x<filesize; x+=1){
		if(buffer[x] == '\0'){
			elements[ncount] = buffer+x+1; // +1 to skip over the null byte.
			ncount += 1;
		}
	}
	
	// Create 1D pixel array - left to right, top to bottom.
	int outputWidth = atoi(elements[0]);
	int outputHeight = atoi(elements[1]);
	rgb_t *pixels = (rgb_t*) malloc(outputWidth * outputHeight * sizeof(rgb_t));
	memset(pixels, '\0', outputWidth * outputHeight * sizeof(rgb_t));
	
	// Begin translation to ppm.
	int index = 2;
	char *position = elements[index];
	while(1){
		if(strcmp(position, "point") == 0){
			
			int y = atoi(elements[index+4]), x = atoi(elements[index+5]);
			rgb_t *pixel = &pixels[y*outputHeight + x];
			pixel->r = (unsigned char) atoi(elements[index+1]);
			pixel->g = (unsigned char) atoi(elements[index+2]);
			pixel->b = (unsigned char) atoi(elements[index+3]);
			
			index += 6; // jump ahead 6 elements
			if(index > count) break;
			position = elements[index];
			
		}else if(strcmp(position, "line") == 0){
			
			int sx = atoi(elements[index+5]), sy = atoi(elements[index+4]);
			int w = atoi(elements[index+7])-sx, h = atoi(elements[index+6])-sy;
			rgb_t color = {
				atoi(elements[index+1]),
				atoi(elements[index+2]),
				atoi(elements[index+3])
			};
			
			// Write the start and end of the line.
			rgb_t *pixel_start = &pixels[sy*outputWidth + sx];
			pixel_start->r = color.r;
			pixel_start->g = color.g;
			pixel_start->b = color.b;
			rgb_t *pixel_end = &pixels[(sy+h)*outputWidth + sx+w];
			pixel_end->r = color.r;
			pixel_end->g = color.g;
			pixel_end->b = color.b;
			
			// Determine the angle of attack.
			double theta = atan2(h, w);
			
			double xStep = cos(theta), yStep = sin(theta);
			double xi = (double) sx;
			double yi = (double) sy;

			double distance = sqrt( w*w + h*h );
			double distanceTraveled = 0;
			
			// Integrate to destination at sx+w,sy+h!
			while(1){
				xi += xStep;
				yi += yStep;
				distanceTraveled += 1;// sin^2(x) + cos^2(x) = 1
				if(distanceTraveled >= distance-1) break;
				
				int cx = round(xi), cy = round(yi);
				rgb_t *pixel = &pixels[cy*outputWidth + cx];
				pixel->r = color.r;
				pixel->g = color.g;
				pixel->b = color.b;
			}
			
			index += 8; // jump ahead 8 elements
			if(index > count) break;
			position = elements[index];
			
		}else if(strcmp(position, "rect") == 0){
			
			int y = atoi(elements[index+4]), x = atoi(elements[index+5]);
			int w = atoi(elements[index+7]), h = atoi(elements[index+6]);
			rgb_t color = {
				atoi(elements[index+1]),
				atoi(elements[index+2]),
				atoi(elements[index+3])
			};
			
			int i,j;
			for(i = y; i<h+y; i+=1){
				for(j = x; j<w+x; j+=1){
					rgb_t *pixel = &pixels[(i)*outputWidth + j];
					pixel->r = color.r;
					pixel->g = color.g;
					pixel->b = color.b;
				}
			}
			
			index += 8; // jump ahead 8 elements
			if(index >= count) break;
			position = elements[index];
			
		}else{
			// Translation finished.
			break;
		}
	}
	
	printf("P3 %s %s 255\n", elements[0], elements[1]);
	printGraph(outputWidth,outputHeight, pixels);
	
	free(buffer);
	free(pixels);
	return 0;
}