clemente di caprio
Library for MI0283QT-2 LCD
Diff: calibrate.c
- Revision:
- 0:7ad454fed160
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/calibrate.c Wed May 23 06:25:31 2012 +0000
@@ -0,0 +1,363 @@
+/*
+ *
+ * Copyright (c) 2001, Carlos E. Vidales. All rights reserved.
+ *
+ * This sample program was written and put in the public domain
+ * by Carlos E. Vidales. The program is provided "as is"
+ * without warranty of any kind, either expressed or implied.
+ * If you choose to use the program within your own products
+ * you do so at your own risk, and assume the responsibility
+ * for servicing, repairing or correcting the program should
+ * it prove defective in any manner.
+ * You may copy and distribute the program's source code in any
+ * medium, provided that you also include in each copy an
+ * appropriate copyright notice and disclaimer of warranty.
+ * You may also modify this program and distribute copies of
+ * it provided that you include prominent notices stating
+ * that you changed the file(s) and the date of any change,
+ * and that you do not charge any royalties or licenses for
+ * its use.
+ *
+ *
+ *
+ * File Name: calibrate.c
+ *
+ *
+ * This file contains functions that implement calculations
+ * necessary to obtain calibration factors for a touch screen
+ * that suffers from multiple distortion effects: namely,
+ * translation, scaling and rotation.
+ *
+ * The following set of equations represent a valid display
+ * point given a corresponding set of touch screen points:
+ *
+ *
+ * /- -\
+ * /- -\ /- -\ | |
+ * | | | | | Xs |
+ * | Xd | | A B C | | |
+ * | | = | | * | Ys |
+ * | Yd | | D E F | | |
+ * | | | | | 1 |
+ * \- -/ \- -/ | |
+ * \- -/
+ *
+ *
+ * where:
+ *
+ * (Xd,Yd) represents the desired display point
+ * coordinates,
+ *
+ * (Xs,Ys) represents the available touch screen
+ * coordinates, and the matrix
+ *
+ * /- -\
+ * |A,B,C|
+ * |D,E,F| represents the factors used to translate
+ * \- -/ the available touch screen point values
+ * into the corresponding display
+ * coordinates.
+ *
+ *
+ * Note that for practical considerations, the utilitities
+ * within this file do not use the matrix coefficients as
+ * defined above, but instead use the following
+ * equivalents, since floating point math is not used:
+ *
+ * A = An/Divider
+ * B = Bn/Divider
+ * C = Cn/Divider
+ * D = Dn/Divider
+ * E = En/Divider
+ * F = Fn/Divider
+ *
+ *
+ *
+ * The functions provided within this file are:
+ *
+ * setCalibrationMatrix() - calculates the set of factors
+ * in the above equation, given
+ * three sets of test points.
+ * getDisplayPoint() - returns the actual display
+ * coordinates, given a set of
+ * touch screen coordinates.
+ * translateRawScreenCoordinates() - helper function to transform
+ * raw screen points into values
+ * scaled to the desired display
+ * resolution.
+ *
+ *
+ */
+
+
+#define _CALIBRATE_C_
+
+
+
+/****************************************************/
+/* */
+/* Included files */
+/* */
+/****************************************************/
+
+#include "calibrate.h"
+
+
+
+/****************************************************/
+/* */
+/* Local Definitions and macros */
+/* */
+/****************************************************/
+
+
+
+/****************************************************/
+/* */
+/* Global variables */
+/* */
+/****************************************************/
+
+
+
+/****************************************************/
+/* */
+/* Forward Declaration of local functions */
+/* */
+/****************************************************/
+
+
+
+
+
+
+/**********************************************************************
+ *
+ * Function: setCalibrationMatrix()
+ *
+ * Description: Calling this function with valid input data
+ * in the display and screen input arguments
+ * causes the calibration factors between the
+ * screen and display points to be calculated,
+ * and the output argument - matrixPtr - to be
+ * populated.
+ *
+ * This function needs to be called only when new
+ * calibration factors are desired.
+ *
+ *
+ * Argument(s): displayPtr (input) - Pointer to an array of three
+ * sample, reference points.
+ * screenPtr (input) - Pointer to the array of touch
+ * screen points corresponding
+ * to the reference display points.
+ * matrixPtr (output) - Pointer to the calibration
+ * matrix computed for the set
+ * of points being provided.
+ *
+ *
+ * From the article text, recall that the matrix coefficients are
+ * resolved to be the following:
+ *
+ *
+ * Divider = (Xs0 - Xs2)*(Ys1 - Ys2) - (Xs1 - Xs2)*(Ys0 - Ys2)
+ *
+ *
+ *
+ * (Xd0 - Xd2)*(Ys1 - Ys2) - (Xd1 - Xd2)*(Ys0 - Ys2)
+ * A = ---------------------------------------------------
+ * Divider
+ *
+ *
+ * (Xs0 - Xs2)*(Xd1 - Xd2) - (Xd0 - Xd2)*(Xs1 - Xs2)
+ * B = ---------------------------------------------------
+ * Divider
+ *
+ *
+ * Ys0*(Xs2*Xd1 - Xs1*Xd2) +
+ * Ys1*(Xs0*Xd2 - Xs2*Xd0) +
+ * Ys2*(Xs1*Xd0 - Xs0*Xd1)
+ * C = ---------------------------------------------------
+ * Divider
+ *
+ *
+ * (Yd0 - Yd2)*(Ys1 - Ys2) - (Yd1 - Yd2)*(Ys0 - Ys2)
+ * D = ---------------------------------------------------
+ * Divider
+ *
+ *
+ * (Xs0 - Xs2)*(Yd1 - Yd2) - (Yd0 - Yd2)*(Xs1 - Xs2)
+ * E = ---------------------------------------------------
+ * Divider
+ *
+ *
+ * Ys0*(Xs2*Yd1 - Xs1*Yd2) +
+ * Ys1*(Xs0*Yd2 - Xs2*Yd0) +
+ * Ys2*(Xs1*Yd0 - Xs0*Yd1)
+ * F = ---------------------------------------------------
+ * Divider
+ *
+ *
+ * Return: OK - the calibration matrix was correctly
+ * calculated and its value is in the
+ * output argument.
+ * NOT_OK - an error was detected and the
+ * function failed to return a valid
+ * set of matrix values.
+ * The only time this sample code returns
+ * NOT_OK is when Divider == 0
+ *
+ *
+ *
+ * NOTE! NOTE! NOTE!
+ *
+ * setCalibrationMatrix() and getDisplayPoint() will do fine
+ * for you as they are, provided that your digitizer
+ * resolution does not exceed 10 bits (1024 values). Higher
+ * resolutions may cause the integer operations to overflow
+ * and return incorrect values. If you wish to use these
+ * functions with digitizer resolutions of 12 bits (4096
+ * values) you will either have to a) use 64-bit signed
+ * integer variables and math, or b) judiciously modify the
+ * operations to scale results by a factor of 2 or even 4.
+ *
+ *
+ */
+unsigned char setCalibrationMatrix( POINT * displayPtr,
+ POINT * screenPtr,
+ MATRIX * matrixPtr)
+{
+
+ unsigned char retValue = OK ;
+
+
+
+ matrixPtr->Divider = ((screenPtr[0].x - screenPtr[2].x) * (screenPtr[1].y - screenPtr[2].y)) -
+ ((screenPtr[1].x - screenPtr[2].x) * (screenPtr[0].y - screenPtr[2].y)) ;
+
+ if( matrixPtr->Divider == 0 )
+ {
+ retValue = NOT_OK ;
+ }
+ else
+ {
+ matrixPtr->An = ((displayPtr[0].x - displayPtr[2].x) * (screenPtr[1].y - screenPtr[2].y)) -
+ ((displayPtr[1].x - displayPtr[2].x) * (screenPtr[0].y - screenPtr[2].y)) ;
+
+ matrixPtr->Bn = ((screenPtr[0].x - screenPtr[2].x) * (displayPtr[1].x - displayPtr[2].x)) -
+ ((displayPtr[0].x - displayPtr[2].x) * (screenPtr[1].x - screenPtr[2].x)) ;
+
+ matrixPtr->Cn = (screenPtr[2].x * displayPtr[1].x - screenPtr[1].x * displayPtr[2].x) * screenPtr[0].y +
+ (screenPtr[0].x * displayPtr[2].x - screenPtr[2].x * displayPtr[0].x) * screenPtr[1].y +
+ (screenPtr[1].x * displayPtr[0].x - screenPtr[0].x * displayPtr[1].x) * screenPtr[2].y ;
+
+ matrixPtr->Dn = ((displayPtr[0].y - displayPtr[2].y) * (screenPtr[1].y - screenPtr[2].y)) -
+ ((displayPtr[1].y - displayPtr[2].y) * (screenPtr[0].y - screenPtr[2].y)) ;
+
+ matrixPtr->En = ((screenPtr[0].x - screenPtr[2].x) * (displayPtr[1].y - displayPtr[2].y)) -
+ ((displayPtr[0].y - displayPtr[2].y) * (screenPtr[1].x - screenPtr[2].x)) ;
+
+ matrixPtr->Fn = (screenPtr[2].x * displayPtr[1].y - screenPtr[1].x * displayPtr[2].y) * screenPtr[0].y +
+ (screenPtr[0].x * displayPtr[2].y - screenPtr[2].x * displayPtr[0].y) * screenPtr[1].y +
+ (screenPtr[1].x * displayPtr[0].y - screenPtr[0].x * displayPtr[1].y) * screenPtr[2].y ;
+ }
+
+ return( retValue ) ;
+
+} /* end of setCalibrationMatrix() */
+
+
+
+/**********************************************************************
+ *
+ * Function: getDisplayPoint()
+ *
+ * Description: Given a valid set of calibration factors and a point
+ * value reported by the touch screen, this function
+ * calculates and returns the true (or closest to true)
+ * display point below the spot where the touch screen
+ * was touched.
+ *
+ *
+ *
+ * Argument(s): displayPtr (output) - Pointer to the calculated
+ * (true) display point.
+ * screenPtr (input) - Pointer to the reported touch
+ * screen point.
+ * matrixPtr (input) - Pointer to calibration factors
+ * matrix previously calculated
+ * from a call to
+ * setCalibrationMatrix()
+ *
+ *
+ * The function simply solves for Xd and Yd by implementing the
+ * computations required by the translation matrix.
+ *
+ * /- -\
+ * /- -\ /- -\ | |
+ * | | | | | Xs |
+ * | Xd | | A B C | | |
+ * | | = | | * | Ys |
+ * | Yd | | D E F | | |
+ * | | | | | 1 |
+ * \- -/ \- -/ | |
+ * \- -/
+ *
+ * It must be kept brief to avoid consuming CPU cycles.
+ *
+ *
+ * Return: OK - the display point was correctly calculated
+ * and its value is in the output argument.
+ * NOT_OK - an error was detected and the function
+ * failed to return a valid point.
+ *
+ *
+ *
+ * NOTE! NOTE! NOTE!
+ *
+ * setCalibrationMatrix() and getDisplayPoint() will do fine
+ * for you as they are, provided that your digitizer
+ * resolution does not exceed 10 bits (1024 values). Higher
+ * resolutions may cause the integer operations to overflow
+ * and return incorrect values. If you wish to use these
+ * functions with digitizer resolutions of 12 bits (4096
+ * values) you will either have to a) use 64-bit signed
+ * integer variables and math, or b) judiciously modify the
+ * operations to scale results by a factor of 2 or even 4.
+ *
+ *
+ */
+unsigned char getDisplayPoint( POINT * displayPtr,
+ POINT * screenPtr,
+ MATRIX * matrixPtr )
+{
+ unsigned char retValue = OK ;
+
+
+ if( matrixPtr->Divider != 0 )
+ {
+
+ /* Operation order is important since we are doing integer */
+ /* math. Make sure you add all terms together before */
+ /* dividing, so that the remainder is not rounded off */
+ /* prematurely. */
+
+ displayPtr->x = ( (matrixPtr->An * screenPtr->x) +
+ (matrixPtr->Bn * screenPtr->y) +
+ matrixPtr->Cn
+ ) / matrixPtr->Divider ;
+
+ displayPtr->y = ( (matrixPtr->Dn * screenPtr->x) +
+ (matrixPtr->En * screenPtr->y) +
+ matrixPtr->Fn
+ ) / matrixPtr->Divider ;
+ }
+ else
+ {
+ retValue = NOT_OK ;
+ }
+
+ return( retValue ) ;
+
+} /* end of getDisplayPoint() */
+