#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>

//Function prototypes

//reads a 640x480 PPM file (specified by filename) and returns a pointer to the image data. It returns NULL on failure
int *readPPMFile(char *fileName); 

//writes the 640x480 image represented by imageData to the file named by fileName in PPM format. Returns 1 on success, 0 on failure
int writePPMFile(char *fileName, int *imageData); 

//blends the blue screen image1 with image2 and returns a pointer to the blended image. Returns NULL on failure
int *blend(int *image1, int *image2); 


//Complete this function
int writePPMFile(char *filename, int *imageData) {

}



//Complete this function
int *blend(int *image1, int *image2) {


}

//DO NOT CHANGE ANYTHING BELOW
//READ THE CODE CAREFULLY 

int main (int argc, char *args[])
{
	//DO NOT MODIFY THIS FUNCTION IN ANY WAY

	//all images are 640x480
	int *image1; //pointer to blue screen image data
	int *image2; //pointer to second image data
	int *image3; //pointer to blended image data
	
	
	image1 = readPPMFile(args[1]); //read blue screen image file
	
	if (image1 == NULL) {
		printf("Problems reading file %s. Exiting...\n", args[1]);
		exit(1);
	}
		
	
	image2 = readPPMFile(args[2]); //read second image file
	
	if (image2 == NULL) {
		printf("Problems reading file %s. Exiting...\n", args[2]);
		exit(1);
	}
	
	image3 = blend(image1, image2); //blend the two images

	int x = writePPMFile(args[3], image3); //write the blended image to the third file

	if (x == 0) {
		printf("Problems writing file %s. Exiting...\n", args[3]);
		exit(1);
	}
		
}

//Open the specified ppm file and return a pointer to an array of ints representing the image data
//return NULL on failure
int *readPPMFile(char *fileName)
{
	char c;
	char imageType[3];
	int *imageData; //pointer to ppm image data read from file
	FILE *fp; //pointer to image file
	int i;
	int w, h, max;
	
	
	fp = fopen(fileName, "r"); //open file for reading. "r" for reading. Use "w" to open file for writing.
	if (fp == NULL) {
		printf("File cannot be opened. Check file name..\n");
		return NULL;
	}
		
	//read magic number
	fscanf (fp, "%s", imageType);
	
	//Stop if image type is not P6
	if (strcmp(imageType,"P6") != 0) {
		printf("Bad image format. Check image format and run again\n");
		return NULL;
	}
		
	//Read and discard characters till you see a newline
	do {
		c = fgetc(fp);
	} while ( c != '\n');

	
	c = fgetc(fp); //Read next character. This may be the # character
	
	if ( c == '#') { //file has a comment
		//Read and discard characters till you see a newline
		do {
			c = fgetc(fp);
			} while ( c != '\n');
		}
	else {// file has no comment
		ungetc(c, fp);
		}
	
	fscanf(fp,"%d %d", &w, &h);
	fscanf(fp, "%d", &max);
	
	
	//Read and discard characters till you see a newline
		do {
			c = fgetc(fp);
			} while ( c != '\n');

	//end of header processing
	
	imageData =  malloc(3*w*h*sizeof(int)); //allocate enough space for all the pixels in the image
	if (imageData == NULL) {
		printf("Problems allocating memory..\n");
		return NULL;
	}
	
	//read the image data into the imageData array
	//note how the pointer "imageData" can also be used as an array
	for(i=0; i < 3*w*h; i+=3)
		fscanf(fp, "%c%c%c", &imageData[i],&imageData[i+1],&imageData[i+2]);
	
	return imageData;
}