Targa.c

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// Licenced under LGPL: www.gnu.org/copyleft/lesser.html
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
main() {

	// Create a new targa image in memory
	char* newImage(int width, int height) {
		char* image = malloc(18+4*width*height+26);
		strcpy(image+18+4*width*height+8,"TRUEVISION-XFILE.");
		image[2] = 2;
		image[12] = width & 0xff;
		image[13] = (width & 0xff00) >> 8;
		image[14] = height & 0xff;
		image[15] = (height & 0xff00) >> 8;
		image[16] = ' ';
		image[17] = 8;
		return image;
		}

	// Return complete byte size of passed image
	int getSize(unsigned char* image) {
		int width = (image[13]<<8)+image[12];
		int height = (image[15]<<8)+image[14];
		return 18+4*width*height+26;
		}

	// Return address of pixel x,y in passed image
	char* getOffset(unsigned char* image, int x, int y) {
		int width = (image[13]<<8)+image[12];
		return image+18+4*(x+y*width);
		}

	// Return the content of pixel x,y for the passed image
	int getPixel(char* image, int x, int y) {
		return *getOffset(image,x,y);
		}

	// Set pixel x,y to passed colour allowing for alpha
	void setPixel(char* image, int x, int y, int colour) {
		int i, col[3], a = colour >> 24;
		col[0] = (colour & 0xff0000) >> 16;
		col[1] = (colour & 0xff00) >> 8;
		col[2] = colour & 0xff;
		unsigned char* pix = getOffset(image,x,y);
		for (i = 0; i < 3; i++)
			pix[i] = (a*col[i]+(255-a)*pix[i])/255;
		}

	// Fill a rect in passed image using passed bounds and colour
	void fillRect(char* image, int x1, int y1, int x2, int y2, int colour) {
		int x,y;
		for (y = y1; y < y2; y++)
			for (x = x1; x < x2; x++)
				setPixel(image,x,y,colour);
		}


	// Create test a image
	char* image = newImage(200,200);
	fillRect(image,50,50,100,100,0xff0000ff);
	fillRect(image,75,75,175,175,0x80ff0000);
	fillRect(image,60,60,165,165,0x40ff00ff);

	// Write test image to file and convert to jpeg
	int fd = creat("/var/www/wiki/targa.tga",0x755);
	write(fd,image,getSize(image));
	system("cjpeg -quality 100 /var/www/wiki/targa.tga > /var/www/wiki/targa.jpg");

	}