calibrate.c

在运行嵌入式Linux系统的、支持屏幕点击功能的手机上

/*
 *  from:
 * 
 *  tslib/tests/ts_calibrate.c
 *
 *  Copyright (C) 2001 Russell King.
 *
 * This file is placed under the GPL.  Please see the file
 * COPYING for more details.
 *
 * $Id: calibrate.c,v 1.1 2005/11/28 06:44:16 chh Exp $
 *
 * Basic test program for touchscreen library.
 */

#include <stdio.h>

#include "calibrate.h"

extern int flag_debug;

int perform_calibration(calibration *cal) {
	int j;
	float n, x, y, x2, y2, xy, z, zx, zy;
	float det, a, b, c, e, f, i;
	float scaling = 65536.0;

// Get sums for matrix
	n = x = y = x2 = y2 = xy = 0;
	for(j=0;j<5;j++) {
		n += 1.0;
		x += (float)cal->x[j];
		y += (float)cal->y[j];
		x2 += (float)(cal->x[j]*cal->x[j]);
		y2 += (float)(cal->y[j]*cal->y[j]);
		xy += (float)(cal->x[j]*cal->y[j]);
	}

// Get determinant of matrix -- check if determinant is too small
	det = n*(x2*y2 - xy*xy) + x*(xy*y - x*y2) + y*(x*xy - y*x2);
	if(det < 0.1 && det > -0.1) {
		fprintf(stderr, "ts_calibrate: determinant is too small -- %f\n",det);
		return 0;
	}

// Get elements of inverse matrix
	a = (x2*y2 - xy*xy)/det;
	b = (xy*y - x*y2)/det;
	c = (x*xy - y*x2)/det;
	e = (n*y2 - y*y)/det;
	f = (x*y - n*xy)/det;
	i = (n*x2 - x*x)/det;

// Get sums for x calibration
	z = zx = zy = 0;
	for(j=0;j<5;j++) {
		z += (float)cal->xfb[j];
		zx += (float)(cal->xfb[j]*cal->x[j]);
		zy += (float)(cal->xfb[j]*cal->y[j]);
	}

// Now multiply out to get the calibration for framebuffer x coord
	cal->a[0] = (int)((a*z + b*zx + c*zy)*(scaling));
	cal->a[1] = (int)((b*z + e*zx + f*zy)*(scaling));
	cal->a[2] = (int)((c*z + f*zx + i*zy)*(scaling));

	if (flag_debug)
	  fprintf(stderr, "%f %f %f\n",(a*z + b*zx + c*zy),
		  (b*z + e*zx + f*zy),
		  (c*z + f*zx + i*zy));

// Get sums for y calibration
	z = zx = zy = 0;
	for(j=0;j<5;j++) {
		z += (float)cal->yfb[j];
		zx += (float)(cal->yfb[j]*cal->x[j]);
		zy += (float)(cal->yfb[j]*cal->y[j]);
	}

// Now multiply out to get the calibration for framebuffer y coord
	cal->a[3] = (int)((a*z + b*zx + c*zy)*(scaling));
	cal->a[4] = (int)((b*z + e*zx + f*zy)*(scaling));
	cal->a[5] = (int)((c*z + f*zx + i*zy)*(scaling));

	if (flag_debug)
	  fprintf(stderr, "%f %f %f\n",(a*z + b*zx + c*zy),
		  (b*z + e*zx + f*zy),
		  (c*z + f*zx + i*zy));

// If we got here, we're OK, so assign scaling to a[6] and return
	cal->a[6] = (int)scaling;
	return 1;
/*	
// This code was here originally to just insert default values
	for(j=0;j<7;j++) {
		c->a[j]=0;
	}
	c->a[1] = c->a[5] = c->a[6] = 1;
	return 1;
*/

}