clemente di caprio
Library for MI0283QT-2 LCD
calibrate.c
- Committer:
- clemente
- Date:
- 2012-05-23
- Revision:
- 0:7ad454fed160
File content as of revision 0:7ad454fed160:
/*
*
* 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() */