#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>

#pragma pack(push, 1)

typedef struct _BITMAPFILEHEADER {
	unsigned short bfType;
	unsigned int bfSize;
	unsigned short bfReserved1;
	unsigned short bfReserved2;
	unsigned int bfOffBits;
} BITMAPFILEHEADER;

typedef struct _BITMAPINFOHEADER {
	unsigned int biSize;
	int biWidth;
	int biHeight;
	unsigned short biPlanes;
	unsigned short biBitCount;
	unsigned int biCompression;
	unsigned int biSizeImage;
	int biXPersPerMeter;
	int biYPersPerMeter;
	unsigned int biClrUsed;
	unsigned int biClrImprotant;
} BITMAPINFOHEADER;

typedef struct _RGBTRIPLE {
	unsigned char rgbtBlue;
	unsigned char rgbtGreen;
	unsigned char rgbtRed;
} RGBTRIPLE;

#pragma pack(pop)

#define PIXEL_SIZE 3
#define PIXEL_ALIGN 4

int main()
{
	FILE* fpBmp;
	FILE* fpTxt;
	BITMAPFILEHEADER fileHeader;
	BITMAPINFOHEADER infoHeader;

	unsigned char* image;
	int size;
	int width, height;
	int padding;

	char ascii[] = { '9','8', '7', '6', '5', '4', '3', '2', '1', '0', ' ' };

	fpBmp = fopen("sample.bmp", "rb");
	if (fpBmp == NULL)
		return 0;

	if (fread(&fileHeader, sizeof(BITMAPFILEHEADER), 1, fpBmp) < 1)
	{
		fclose(fpBmp);
		return 0;
	}

	if (fileHeader.bfType != 'MB')
	{
		fclose(fpBmp);
		return 0;
	}

	if (fread(&infoHeader, sizeof(BITMAPINFOHEADER), 1, fpBmp) < 1)
	{
		fclose(fpBmp);
		return 0;
	}

	if (infoHeader.biBitCount != 24)
	{
		fclose(fpBmp);
		return 0;
	}

	size = infoHeader.biSizeImage;
	width = infoHeader.biWidth;
	height = infoHeader.biHeight;

	padding = (PIXEL_ALIGN - (width * PIXEL_SIZE) % PIXEL_ALIGN) % PIXEL_ALIGN;

	if (size == 0)
	{
		size = (width * PIXEL_ALIGN + padding) * height;
	}

	image = malloc(size);

	fseek(fpBmp, fileHeader.bfOffBits, SEEK_SET);

	if (fread(image, size, 1, fpBmp) < 1)
	{
		fclose(fpBmp);
		return 0;
	}

	fclose(fpBmp);

	//fpTxt = fopen("sample.txt", "w");
	fpTxt = stdout;
	if (fpTxt == NULL)
	{
		free(image);
		return 0;
	}

	for (int y = height - 1; y >= 0; y--)
	{
		for (int x = 0; x < width; x++)
		{
			int index = (x * PIXEL_SIZE) + (y * (width * PIXEL_SIZE)) + (padding * y);

			RGBTRIPLE* pixel = (RGBTRIPLE*)&image[index];

			unsigned char blue = pixel->rgbtBlue;
			unsigned char green = pixel->rgbtGreen;
			unsigned char red = pixel->rgbtRed;

			unsigned char gray = (red + green + blue) / PIXEL_SIZE;

			char c = ascii[gray * sizeof(ascii) / 256];

			fprintf(fpTxt, "%c", c);
		}
		fprintf(fpTxt, "\n");
	}

	fclose(fpTxt);

	free(image);

	return 0;
}