Library for MI0283QT-2 LCD
calibrate.c@0:7ad454fed160, 2012-05-23 (annotated)
- Committer:
- clemente
- Date:
- Wed May 23 06:25:31 2012 +0000
- Revision:
- 0:7ad454fed160
Who changed what in which revision?
User | Revision | Line number | New contents of line |
---|---|---|---|
clemente | 0:7ad454fed160 | 1 | /* |
clemente | 0:7ad454fed160 | 2 | * |
clemente | 0:7ad454fed160 | 3 | * Copyright (c) 2001, Carlos E. Vidales. All rights reserved. |
clemente | 0:7ad454fed160 | 4 | * |
clemente | 0:7ad454fed160 | 5 | * This sample program was written and put in the public domain |
clemente | 0:7ad454fed160 | 6 | * by Carlos E. Vidales. The program is provided "as is" |
clemente | 0:7ad454fed160 | 7 | * without warranty of any kind, either expressed or implied. |
clemente | 0:7ad454fed160 | 8 | * If you choose to use the program within your own products |
clemente | 0:7ad454fed160 | 9 | * you do so at your own risk, and assume the responsibility |
clemente | 0:7ad454fed160 | 10 | * for servicing, repairing or correcting the program should |
clemente | 0:7ad454fed160 | 11 | * it prove defective in any manner. |
clemente | 0:7ad454fed160 | 12 | * You may copy and distribute the program's source code in any |
clemente | 0:7ad454fed160 | 13 | * medium, provided that you also include in each copy an |
clemente | 0:7ad454fed160 | 14 | * appropriate copyright notice and disclaimer of warranty. |
clemente | 0:7ad454fed160 | 15 | * You may also modify this program and distribute copies of |
clemente | 0:7ad454fed160 | 16 | * it provided that you include prominent notices stating |
clemente | 0:7ad454fed160 | 17 | * that you changed the file(s) and the date of any change, |
clemente | 0:7ad454fed160 | 18 | * and that you do not charge any royalties or licenses for |
clemente | 0:7ad454fed160 | 19 | * its use. |
clemente | 0:7ad454fed160 | 20 | * |
clemente | 0:7ad454fed160 | 21 | * |
clemente | 0:7ad454fed160 | 22 | * |
clemente | 0:7ad454fed160 | 23 | * File Name: calibrate.c |
clemente | 0:7ad454fed160 | 24 | * |
clemente | 0:7ad454fed160 | 25 | * |
clemente | 0:7ad454fed160 | 26 | * This file contains functions that implement calculations |
clemente | 0:7ad454fed160 | 27 | * necessary to obtain calibration factors for a touch screen |
clemente | 0:7ad454fed160 | 28 | * that suffers from multiple distortion effects: namely, |
clemente | 0:7ad454fed160 | 29 | * translation, scaling and rotation. |
clemente | 0:7ad454fed160 | 30 | * |
clemente | 0:7ad454fed160 | 31 | * The following set of equations represent a valid display |
clemente | 0:7ad454fed160 | 32 | * point given a corresponding set of touch screen points: |
clemente | 0:7ad454fed160 | 33 | * |
clemente | 0:7ad454fed160 | 34 | * |
clemente | 0:7ad454fed160 | 35 | * /- -\ |
clemente | 0:7ad454fed160 | 36 | * /- -\ /- -\ | | |
clemente | 0:7ad454fed160 | 37 | * | | | | | Xs | |
clemente | 0:7ad454fed160 | 38 | * | Xd | | A B C | | | |
clemente | 0:7ad454fed160 | 39 | * | | = | | * | Ys | |
clemente | 0:7ad454fed160 | 40 | * | Yd | | D E F | | | |
clemente | 0:7ad454fed160 | 41 | * | | | | | 1 | |
clemente | 0:7ad454fed160 | 42 | * \- -/ \- -/ | | |
clemente | 0:7ad454fed160 | 43 | * \- -/ |
clemente | 0:7ad454fed160 | 44 | * |
clemente | 0:7ad454fed160 | 45 | * |
clemente | 0:7ad454fed160 | 46 | * where: |
clemente | 0:7ad454fed160 | 47 | * |
clemente | 0:7ad454fed160 | 48 | * (Xd,Yd) represents the desired display point |
clemente | 0:7ad454fed160 | 49 | * coordinates, |
clemente | 0:7ad454fed160 | 50 | * |
clemente | 0:7ad454fed160 | 51 | * (Xs,Ys) represents the available touch screen |
clemente | 0:7ad454fed160 | 52 | * coordinates, and the matrix |
clemente | 0:7ad454fed160 | 53 | * |
clemente | 0:7ad454fed160 | 54 | * /- -\ |
clemente | 0:7ad454fed160 | 55 | * |A,B,C| |
clemente | 0:7ad454fed160 | 56 | * |D,E,F| represents the factors used to translate |
clemente | 0:7ad454fed160 | 57 | * \- -/ the available touch screen point values |
clemente | 0:7ad454fed160 | 58 | * into the corresponding display |
clemente | 0:7ad454fed160 | 59 | * coordinates. |
clemente | 0:7ad454fed160 | 60 | * |
clemente | 0:7ad454fed160 | 61 | * |
clemente | 0:7ad454fed160 | 62 | * Note that for practical considerations, the utilitities |
clemente | 0:7ad454fed160 | 63 | * within this file do not use the matrix coefficients as |
clemente | 0:7ad454fed160 | 64 | * defined above, but instead use the following |
clemente | 0:7ad454fed160 | 65 | * equivalents, since floating point math is not used: |
clemente | 0:7ad454fed160 | 66 | * |
clemente | 0:7ad454fed160 | 67 | * A = An/Divider |
clemente | 0:7ad454fed160 | 68 | * B = Bn/Divider |
clemente | 0:7ad454fed160 | 69 | * C = Cn/Divider |
clemente | 0:7ad454fed160 | 70 | * D = Dn/Divider |
clemente | 0:7ad454fed160 | 71 | * E = En/Divider |
clemente | 0:7ad454fed160 | 72 | * F = Fn/Divider |
clemente | 0:7ad454fed160 | 73 | * |
clemente | 0:7ad454fed160 | 74 | * |
clemente | 0:7ad454fed160 | 75 | * |
clemente | 0:7ad454fed160 | 76 | * The functions provided within this file are: |
clemente | 0:7ad454fed160 | 77 | * |
clemente | 0:7ad454fed160 | 78 | * setCalibrationMatrix() - calculates the set of factors |
clemente | 0:7ad454fed160 | 79 | * in the above equation, given |
clemente | 0:7ad454fed160 | 80 | * three sets of test points. |
clemente | 0:7ad454fed160 | 81 | * getDisplayPoint() - returns the actual display |
clemente | 0:7ad454fed160 | 82 | * coordinates, given a set of |
clemente | 0:7ad454fed160 | 83 | * touch screen coordinates. |
clemente | 0:7ad454fed160 | 84 | * translateRawScreenCoordinates() - helper function to transform |
clemente | 0:7ad454fed160 | 85 | * raw screen points into values |
clemente | 0:7ad454fed160 | 86 | * scaled to the desired display |
clemente | 0:7ad454fed160 | 87 | * resolution. |
clemente | 0:7ad454fed160 | 88 | * |
clemente | 0:7ad454fed160 | 89 | * |
clemente | 0:7ad454fed160 | 90 | */ |
clemente | 0:7ad454fed160 | 91 | |
clemente | 0:7ad454fed160 | 92 | |
clemente | 0:7ad454fed160 | 93 | #define _CALIBRATE_C_ |
clemente | 0:7ad454fed160 | 94 | |
clemente | 0:7ad454fed160 | 95 | |
clemente | 0:7ad454fed160 | 96 | |
clemente | 0:7ad454fed160 | 97 | /****************************************************/ |
clemente | 0:7ad454fed160 | 98 | /* */ |
clemente | 0:7ad454fed160 | 99 | /* Included files */ |
clemente | 0:7ad454fed160 | 100 | /* */ |
clemente | 0:7ad454fed160 | 101 | /****************************************************/ |
clemente | 0:7ad454fed160 | 102 | |
clemente | 0:7ad454fed160 | 103 | #include "calibrate.h" |
clemente | 0:7ad454fed160 | 104 | |
clemente | 0:7ad454fed160 | 105 | |
clemente | 0:7ad454fed160 | 106 | |
clemente | 0:7ad454fed160 | 107 | /****************************************************/ |
clemente | 0:7ad454fed160 | 108 | /* */ |
clemente | 0:7ad454fed160 | 109 | /* Local Definitions and macros */ |
clemente | 0:7ad454fed160 | 110 | /* */ |
clemente | 0:7ad454fed160 | 111 | /****************************************************/ |
clemente | 0:7ad454fed160 | 112 | |
clemente | 0:7ad454fed160 | 113 | |
clemente | 0:7ad454fed160 | 114 | |
clemente | 0:7ad454fed160 | 115 | /****************************************************/ |
clemente | 0:7ad454fed160 | 116 | /* */ |
clemente | 0:7ad454fed160 | 117 | /* Global variables */ |
clemente | 0:7ad454fed160 | 118 | /* */ |
clemente | 0:7ad454fed160 | 119 | /****************************************************/ |
clemente | 0:7ad454fed160 | 120 | |
clemente | 0:7ad454fed160 | 121 | |
clemente | 0:7ad454fed160 | 122 | |
clemente | 0:7ad454fed160 | 123 | /****************************************************/ |
clemente | 0:7ad454fed160 | 124 | /* */ |
clemente | 0:7ad454fed160 | 125 | /* Forward Declaration of local functions */ |
clemente | 0:7ad454fed160 | 126 | /* */ |
clemente | 0:7ad454fed160 | 127 | /****************************************************/ |
clemente | 0:7ad454fed160 | 128 | |
clemente | 0:7ad454fed160 | 129 | |
clemente | 0:7ad454fed160 | 130 | |
clemente | 0:7ad454fed160 | 131 | |
clemente | 0:7ad454fed160 | 132 | |
clemente | 0:7ad454fed160 | 133 | |
clemente | 0:7ad454fed160 | 134 | /********************************************************************** |
clemente | 0:7ad454fed160 | 135 | * |
clemente | 0:7ad454fed160 | 136 | * Function: setCalibrationMatrix() |
clemente | 0:7ad454fed160 | 137 | * |
clemente | 0:7ad454fed160 | 138 | * Description: Calling this function with valid input data |
clemente | 0:7ad454fed160 | 139 | * in the display and screen input arguments |
clemente | 0:7ad454fed160 | 140 | * causes the calibration factors between the |
clemente | 0:7ad454fed160 | 141 | * screen and display points to be calculated, |
clemente | 0:7ad454fed160 | 142 | * and the output argument - matrixPtr - to be |
clemente | 0:7ad454fed160 | 143 | * populated. |
clemente | 0:7ad454fed160 | 144 | * |
clemente | 0:7ad454fed160 | 145 | * This function needs to be called only when new |
clemente | 0:7ad454fed160 | 146 | * calibration factors are desired. |
clemente | 0:7ad454fed160 | 147 | * |
clemente | 0:7ad454fed160 | 148 | * |
clemente | 0:7ad454fed160 | 149 | * Argument(s): displayPtr (input) - Pointer to an array of three |
clemente | 0:7ad454fed160 | 150 | * sample, reference points. |
clemente | 0:7ad454fed160 | 151 | * screenPtr (input) - Pointer to the array of touch |
clemente | 0:7ad454fed160 | 152 | * screen points corresponding |
clemente | 0:7ad454fed160 | 153 | * to the reference display points. |
clemente | 0:7ad454fed160 | 154 | * matrixPtr (output) - Pointer to the calibration |
clemente | 0:7ad454fed160 | 155 | * matrix computed for the set |
clemente | 0:7ad454fed160 | 156 | * of points being provided. |
clemente | 0:7ad454fed160 | 157 | * |
clemente | 0:7ad454fed160 | 158 | * |
clemente | 0:7ad454fed160 | 159 | * From the article text, recall that the matrix coefficients are |
clemente | 0:7ad454fed160 | 160 | * resolved to be the following: |
clemente | 0:7ad454fed160 | 161 | * |
clemente | 0:7ad454fed160 | 162 | * |
clemente | 0:7ad454fed160 | 163 | * Divider = (Xs0 - Xs2)*(Ys1 - Ys2) - (Xs1 - Xs2)*(Ys0 - Ys2) |
clemente | 0:7ad454fed160 | 164 | * |
clemente | 0:7ad454fed160 | 165 | * |
clemente | 0:7ad454fed160 | 166 | * |
clemente | 0:7ad454fed160 | 167 | * (Xd0 - Xd2)*(Ys1 - Ys2) - (Xd1 - Xd2)*(Ys0 - Ys2) |
clemente | 0:7ad454fed160 | 168 | * A = --------------------------------------------------- |
clemente | 0:7ad454fed160 | 169 | * Divider |
clemente | 0:7ad454fed160 | 170 | * |
clemente | 0:7ad454fed160 | 171 | * |
clemente | 0:7ad454fed160 | 172 | * (Xs0 - Xs2)*(Xd1 - Xd2) - (Xd0 - Xd2)*(Xs1 - Xs2) |
clemente | 0:7ad454fed160 | 173 | * B = --------------------------------------------------- |
clemente | 0:7ad454fed160 | 174 | * Divider |
clemente | 0:7ad454fed160 | 175 | * |
clemente | 0:7ad454fed160 | 176 | * |
clemente | 0:7ad454fed160 | 177 | * Ys0*(Xs2*Xd1 - Xs1*Xd2) + |
clemente | 0:7ad454fed160 | 178 | * Ys1*(Xs0*Xd2 - Xs2*Xd0) + |
clemente | 0:7ad454fed160 | 179 | * Ys2*(Xs1*Xd0 - Xs0*Xd1) |
clemente | 0:7ad454fed160 | 180 | * C = --------------------------------------------------- |
clemente | 0:7ad454fed160 | 181 | * Divider |
clemente | 0:7ad454fed160 | 182 | * |
clemente | 0:7ad454fed160 | 183 | * |
clemente | 0:7ad454fed160 | 184 | * (Yd0 - Yd2)*(Ys1 - Ys2) - (Yd1 - Yd2)*(Ys0 - Ys2) |
clemente | 0:7ad454fed160 | 185 | * D = --------------------------------------------------- |
clemente | 0:7ad454fed160 | 186 | * Divider |
clemente | 0:7ad454fed160 | 187 | * |
clemente | 0:7ad454fed160 | 188 | * |
clemente | 0:7ad454fed160 | 189 | * (Xs0 - Xs2)*(Yd1 - Yd2) - (Yd0 - Yd2)*(Xs1 - Xs2) |
clemente | 0:7ad454fed160 | 190 | * E = --------------------------------------------------- |
clemente | 0:7ad454fed160 | 191 | * Divider |
clemente | 0:7ad454fed160 | 192 | * |
clemente | 0:7ad454fed160 | 193 | * |
clemente | 0:7ad454fed160 | 194 | * Ys0*(Xs2*Yd1 - Xs1*Yd2) + |
clemente | 0:7ad454fed160 | 195 | * Ys1*(Xs0*Yd2 - Xs2*Yd0) + |
clemente | 0:7ad454fed160 | 196 | * Ys2*(Xs1*Yd0 - Xs0*Yd1) |
clemente | 0:7ad454fed160 | 197 | * F = --------------------------------------------------- |
clemente | 0:7ad454fed160 | 198 | * Divider |
clemente | 0:7ad454fed160 | 199 | * |
clemente | 0:7ad454fed160 | 200 | * |
clemente | 0:7ad454fed160 | 201 | * Return: OK - the calibration matrix was correctly |
clemente | 0:7ad454fed160 | 202 | * calculated and its value is in the |
clemente | 0:7ad454fed160 | 203 | * output argument. |
clemente | 0:7ad454fed160 | 204 | * NOT_OK - an error was detected and the |
clemente | 0:7ad454fed160 | 205 | * function failed to return a valid |
clemente | 0:7ad454fed160 | 206 | * set of matrix values. |
clemente | 0:7ad454fed160 | 207 | * The only time this sample code returns |
clemente | 0:7ad454fed160 | 208 | * NOT_OK is when Divider == 0 |
clemente | 0:7ad454fed160 | 209 | * |
clemente | 0:7ad454fed160 | 210 | * |
clemente | 0:7ad454fed160 | 211 | * |
clemente | 0:7ad454fed160 | 212 | * NOTE! NOTE! NOTE! |
clemente | 0:7ad454fed160 | 213 | * |
clemente | 0:7ad454fed160 | 214 | * setCalibrationMatrix() and getDisplayPoint() will do fine |
clemente | 0:7ad454fed160 | 215 | * for you as they are, provided that your digitizer |
clemente | 0:7ad454fed160 | 216 | * resolution does not exceed 10 bits (1024 values). Higher |
clemente | 0:7ad454fed160 | 217 | * resolutions may cause the integer operations to overflow |
clemente | 0:7ad454fed160 | 218 | * and return incorrect values. If you wish to use these |
clemente | 0:7ad454fed160 | 219 | * functions with digitizer resolutions of 12 bits (4096 |
clemente | 0:7ad454fed160 | 220 | * values) you will either have to a) use 64-bit signed |
clemente | 0:7ad454fed160 | 221 | * integer variables and math, or b) judiciously modify the |
clemente | 0:7ad454fed160 | 222 | * operations to scale results by a factor of 2 or even 4. |
clemente | 0:7ad454fed160 | 223 | * |
clemente | 0:7ad454fed160 | 224 | * |
clemente | 0:7ad454fed160 | 225 | */ |
clemente | 0:7ad454fed160 | 226 | unsigned char setCalibrationMatrix( POINT * displayPtr, |
clemente | 0:7ad454fed160 | 227 | POINT * screenPtr, |
clemente | 0:7ad454fed160 | 228 | MATRIX * matrixPtr) |
clemente | 0:7ad454fed160 | 229 | { |
clemente | 0:7ad454fed160 | 230 | |
clemente | 0:7ad454fed160 | 231 | unsigned char retValue = OK ; |
clemente | 0:7ad454fed160 | 232 | |
clemente | 0:7ad454fed160 | 233 | |
clemente | 0:7ad454fed160 | 234 | |
clemente | 0:7ad454fed160 | 235 | matrixPtr->Divider = ((screenPtr[0].x - screenPtr[2].x) * (screenPtr[1].y - screenPtr[2].y)) - |
clemente | 0:7ad454fed160 | 236 | ((screenPtr[1].x - screenPtr[2].x) * (screenPtr[0].y - screenPtr[2].y)) ; |
clemente | 0:7ad454fed160 | 237 | |
clemente | 0:7ad454fed160 | 238 | if( matrixPtr->Divider == 0 ) |
clemente | 0:7ad454fed160 | 239 | { |
clemente | 0:7ad454fed160 | 240 | retValue = NOT_OK ; |
clemente | 0:7ad454fed160 | 241 | } |
clemente | 0:7ad454fed160 | 242 | else |
clemente | 0:7ad454fed160 | 243 | { |
clemente | 0:7ad454fed160 | 244 | matrixPtr->An = ((displayPtr[0].x - displayPtr[2].x) * (screenPtr[1].y - screenPtr[2].y)) - |
clemente | 0:7ad454fed160 | 245 | ((displayPtr[1].x - displayPtr[2].x) * (screenPtr[0].y - screenPtr[2].y)) ; |
clemente | 0:7ad454fed160 | 246 | |
clemente | 0:7ad454fed160 | 247 | matrixPtr->Bn = ((screenPtr[0].x - screenPtr[2].x) * (displayPtr[1].x - displayPtr[2].x)) - |
clemente | 0:7ad454fed160 | 248 | ((displayPtr[0].x - displayPtr[2].x) * (screenPtr[1].x - screenPtr[2].x)) ; |
clemente | 0:7ad454fed160 | 249 | |
clemente | 0:7ad454fed160 | 250 | matrixPtr->Cn = (screenPtr[2].x * displayPtr[1].x - screenPtr[1].x * displayPtr[2].x) * screenPtr[0].y + |
clemente | 0:7ad454fed160 | 251 | (screenPtr[0].x * displayPtr[2].x - screenPtr[2].x * displayPtr[0].x) * screenPtr[1].y + |
clemente | 0:7ad454fed160 | 252 | (screenPtr[1].x * displayPtr[0].x - screenPtr[0].x * displayPtr[1].x) * screenPtr[2].y ; |
clemente | 0:7ad454fed160 | 253 | |
clemente | 0:7ad454fed160 | 254 | matrixPtr->Dn = ((displayPtr[0].y - displayPtr[2].y) * (screenPtr[1].y - screenPtr[2].y)) - |
clemente | 0:7ad454fed160 | 255 | ((displayPtr[1].y - displayPtr[2].y) * (screenPtr[0].y - screenPtr[2].y)) ; |
clemente | 0:7ad454fed160 | 256 | |
clemente | 0:7ad454fed160 | 257 | matrixPtr->En = ((screenPtr[0].x - screenPtr[2].x) * (displayPtr[1].y - displayPtr[2].y)) - |
clemente | 0:7ad454fed160 | 258 | ((displayPtr[0].y - displayPtr[2].y) * (screenPtr[1].x - screenPtr[2].x)) ; |
clemente | 0:7ad454fed160 | 259 | |
clemente | 0:7ad454fed160 | 260 | matrixPtr->Fn = (screenPtr[2].x * displayPtr[1].y - screenPtr[1].x * displayPtr[2].y) * screenPtr[0].y + |
clemente | 0:7ad454fed160 | 261 | (screenPtr[0].x * displayPtr[2].y - screenPtr[2].x * displayPtr[0].y) * screenPtr[1].y + |
clemente | 0:7ad454fed160 | 262 | (screenPtr[1].x * displayPtr[0].y - screenPtr[0].x * displayPtr[1].y) * screenPtr[2].y ; |
clemente | 0:7ad454fed160 | 263 | } |
clemente | 0:7ad454fed160 | 264 | |
clemente | 0:7ad454fed160 | 265 | return( retValue ) ; |
clemente | 0:7ad454fed160 | 266 | |
clemente | 0:7ad454fed160 | 267 | } /* end of setCalibrationMatrix() */ |
clemente | 0:7ad454fed160 | 268 | |
clemente | 0:7ad454fed160 | 269 | |
clemente | 0:7ad454fed160 | 270 | |
clemente | 0:7ad454fed160 | 271 | /********************************************************************** |
clemente | 0:7ad454fed160 | 272 | * |
clemente | 0:7ad454fed160 | 273 | * Function: getDisplayPoint() |
clemente | 0:7ad454fed160 | 274 | * |
clemente | 0:7ad454fed160 | 275 | * Description: Given a valid set of calibration factors and a point |
clemente | 0:7ad454fed160 | 276 | * value reported by the touch screen, this function |
clemente | 0:7ad454fed160 | 277 | * calculates and returns the true (or closest to true) |
clemente | 0:7ad454fed160 | 278 | * display point below the spot where the touch screen |
clemente | 0:7ad454fed160 | 279 | * was touched. |
clemente | 0:7ad454fed160 | 280 | * |
clemente | 0:7ad454fed160 | 281 | * |
clemente | 0:7ad454fed160 | 282 | * |
clemente | 0:7ad454fed160 | 283 | * Argument(s): displayPtr (output) - Pointer to the calculated |
clemente | 0:7ad454fed160 | 284 | * (true) display point. |
clemente | 0:7ad454fed160 | 285 | * screenPtr (input) - Pointer to the reported touch |
clemente | 0:7ad454fed160 | 286 | * screen point. |
clemente | 0:7ad454fed160 | 287 | * matrixPtr (input) - Pointer to calibration factors |
clemente | 0:7ad454fed160 | 288 | * matrix previously calculated |
clemente | 0:7ad454fed160 | 289 | * from a call to |
clemente | 0:7ad454fed160 | 290 | * setCalibrationMatrix() |
clemente | 0:7ad454fed160 | 291 | * |
clemente | 0:7ad454fed160 | 292 | * |
clemente | 0:7ad454fed160 | 293 | * The function simply solves for Xd and Yd by implementing the |
clemente | 0:7ad454fed160 | 294 | * computations required by the translation matrix. |
clemente | 0:7ad454fed160 | 295 | * |
clemente | 0:7ad454fed160 | 296 | * /- -\ |
clemente | 0:7ad454fed160 | 297 | * /- -\ /- -\ | | |
clemente | 0:7ad454fed160 | 298 | * | | | | | Xs | |
clemente | 0:7ad454fed160 | 299 | * | Xd | | A B C | | | |
clemente | 0:7ad454fed160 | 300 | * | | = | | * | Ys | |
clemente | 0:7ad454fed160 | 301 | * | Yd | | D E F | | | |
clemente | 0:7ad454fed160 | 302 | * | | | | | 1 | |
clemente | 0:7ad454fed160 | 303 | * \- -/ \- -/ | | |
clemente | 0:7ad454fed160 | 304 | * \- -/ |
clemente | 0:7ad454fed160 | 305 | * |
clemente | 0:7ad454fed160 | 306 | * It must be kept brief to avoid consuming CPU cycles. |
clemente | 0:7ad454fed160 | 307 | * |
clemente | 0:7ad454fed160 | 308 | * |
clemente | 0:7ad454fed160 | 309 | * Return: OK - the display point was correctly calculated |
clemente | 0:7ad454fed160 | 310 | * and its value is in the output argument. |
clemente | 0:7ad454fed160 | 311 | * NOT_OK - an error was detected and the function |
clemente | 0:7ad454fed160 | 312 | * failed to return a valid point. |
clemente | 0:7ad454fed160 | 313 | * |
clemente | 0:7ad454fed160 | 314 | * |
clemente | 0:7ad454fed160 | 315 | * |
clemente | 0:7ad454fed160 | 316 | * NOTE! NOTE! NOTE! |
clemente | 0:7ad454fed160 | 317 | * |
clemente | 0:7ad454fed160 | 318 | * setCalibrationMatrix() and getDisplayPoint() will do fine |
clemente | 0:7ad454fed160 | 319 | * for you as they are, provided that your digitizer |
clemente | 0:7ad454fed160 | 320 | * resolution does not exceed 10 bits (1024 values). Higher |
clemente | 0:7ad454fed160 | 321 | * resolutions may cause the integer operations to overflow |
clemente | 0:7ad454fed160 | 322 | * and return incorrect values. If you wish to use these |
clemente | 0:7ad454fed160 | 323 | * functions with digitizer resolutions of 12 bits (4096 |
clemente | 0:7ad454fed160 | 324 | * values) you will either have to a) use 64-bit signed |
clemente | 0:7ad454fed160 | 325 | * integer variables and math, or b) judiciously modify the |
clemente | 0:7ad454fed160 | 326 | * operations to scale results by a factor of 2 or even 4. |
clemente | 0:7ad454fed160 | 327 | * |
clemente | 0:7ad454fed160 | 328 | * |
clemente | 0:7ad454fed160 | 329 | */ |
clemente | 0:7ad454fed160 | 330 | unsigned char getDisplayPoint( POINT * displayPtr, |
clemente | 0:7ad454fed160 | 331 | POINT * screenPtr, |
clemente | 0:7ad454fed160 | 332 | MATRIX * matrixPtr ) |
clemente | 0:7ad454fed160 | 333 | { |
clemente | 0:7ad454fed160 | 334 | unsigned char retValue = OK ; |
clemente | 0:7ad454fed160 | 335 | |
clemente | 0:7ad454fed160 | 336 | |
clemente | 0:7ad454fed160 | 337 | if( matrixPtr->Divider != 0 ) |
clemente | 0:7ad454fed160 | 338 | { |
clemente | 0:7ad454fed160 | 339 | |
clemente | 0:7ad454fed160 | 340 | /* Operation order is important since we are doing integer */ |
clemente | 0:7ad454fed160 | 341 | /* math. Make sure you add all terms together before */ |
clemente | 0:7ad454fed160 | 342 | /* dividing, so that the remainder is not rounded off */ |
clemente | 0:7ad454fed160 | 343 | /* prematurely. */ |
clemente | 0:7ad454fed160 | 344 | |
clemente | 0:7ad454fed160 | 345 | displayPtr->x = ( (matrixPtr->An * screenPtr->x) + |
clemente | 0:7ad454fed160 | 346 | (matrixPtr->Bn * screenPtr->y) + |
clemente | 0:7ad454fed160 | 347 | matrixPtr->Cn |
clemente | 0:7ad454fed160 | 348 | ) / matrixPtr->Divider ; |
clemente | 0:7ad454fed160 | 349 | |
clemente | 0:7ad454fed160 | 350 | displayPtr->y = ( (matrixPtr->Dn * screenPtr->x) + |
clemente | 0:7ad454fed160 | 351 | (matrixPtr->En * screenPtr->y) + |
clemente | 0:7ad454fed160 | 352 | matrixPtr->Fn |
clemente | 0:7ad454fed160 | 353 | ) / matrixPtr->Divider ; |
clemente | 0:7ad454fed160 | 354 | } |
clemente | 0:7ad454fed160 | 355 | else |
clemente | 0:7ad454fed160 | 356 | { |
clemente | 0:7ad454fed160 | 357 | retValue = NOT_OK ; |
clemente | 0:7ad454fed160 | 358 | } |
clemente | 0:7ad454fed160 | 359 | |
clemente | 0:7ad454fed160 | 360 | return( retValue ) ; |
clemente | 0:7ad454fed160 | 361 | |
clemente | 0:7ad454fed160 | 362 | } /* end of getDisplayPoint() */ |
clemente | 0:7ad454fed160 | 363 |