Targa.c

Legacy: This article describes a concept that has been superseded in the course of ongoing development on the Organic Design wiki. Please do not develop this any further or base work on this concept, this is only useful for a historic record of work done. You may find a link to the currently used concept or function in this article, if not you can contact the author to find out what has taken the place of this legacy item.

// 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");

	}