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qgscubicrasterresampler.cpp
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1 /***************************************************************************
2  qgscubicrasterresampler.cpp
3  ----------------------------
4  begin : December 2011
5  copyright : (C) 2011 by Marco Hugentobler
6  email : marco at sourcepole dot ch
7  ***************************************************************************/
8 
9 /***************************************************************************
10  * *
11  * This program is free software; you can redistribute it and/or modify *
12  * it under the terms of the GNU General Public License as published by *
13  * the Free Software Foundation; either version 2 of the License, or *
14  * (at your option) any later version. *
15  * *
16  ***************************************************************************/
17 
19 #include <QImage>
20 #include <qmath.h>
21 
23 // red
24  : cRed00( 0.0 ), cRed10( 0.0 ), cRed20( 0.0 ), cRed30( 0.0 ), cRed01( 0.0 ), cRed11( 0.0 ), cRed21( 0.0 ), cRed31( 0.0 )
25  , cRed02( 0.0 ), cRed12( 0.0 ), cRed22( 0.0 ), cRed32( 0.0 ), cRed03( 0.0 ), cRed13( 0.0 ), cRed23( 0.0 ), cRed33( 0.0 )
26  // green
27  , cGreen00( 0.0 ), cGreen10( 0.0 ), cGreen20( 0.0 ), cGreen30( 0.0 ), cGreen01( 0.0 ), cGreen11( 0.0 ), cGreen21( 0.0 ), cGreen31( 0.0 )
28  , cGreen02( 0.0 ), cGreen12( 0.0 ), cGreen22( 0.0 ), cGreen32( 0.0 ), cGreen03( 0.0 ), cGreen13( 0.0 ), cGreen23( 0.0 ), cGreen33( 0.0 )
29  // blue
30  , cBlue00( 0.0 ), cBlue10( 0.0 ), cBlue20( 0.0 ), cBlue30( 0.0 ), cBlue01( 0.0 ), cBlue11( 0.0 ), cBlue21( 0.0 ), cBlue31( 0.0 )
31  , cBlue02( 0.0 ), cBlue12( 0.0 ), cBlue22( 0.0 ), cBlue32( 0.0 ), cBlue03( 0.0 ), cBlue13( 0.0 ), cBlue23( 0.0 ), cBlue33( 0.0 )
32  // alpha
33  , cAlpha00( 0.0 ), cAlpha10( 0.0 ), cAlpha20( 0.0 ), cAlpha30( 0.0 ), cAlpha01( 0.0 ), cAlpha11( 0.0 ), cAlpha21( 0.0 ), cAlpha31( 0.0 )
34  , cAlpha02( 0.0 ), cAlpha12( 0.0 ), cAlpha22( 0.0 ), cAlpha32( 0.0 ), cAlpha03( 0.0 ), cAlpha13( 0.0 ), cAlpha23( 0.0 ), cAlpha33( 0.0 )
35 {
36 }
37 
39 {
40 }
41 
43 {
44  return new QgsCubicRasterResampler();
45 }
46 
47 void QgsCubicRasterResampler::resample( const QImage& srcImage, QImage& dstImage )
48 {
49  int nCols = srcImage.width();
50  int nRows = srcImage.height();
51 
52  int pos = 0;
53  QRgb px;
54  int *redMatrix = new int[ nCols * nRows ];
55  int *greenMatrix = new int[ nCols * nRows ];
56  int *blueMatrix = new int[ nCols * nRows ];
57  int *alphaMatrix = new int[ nCols * nRows ];
58 
59  for ( int heightIndex = 0; heightIndex < nRows; ++heightIndex )
60  {
61  QRgb* scanLine = ( QRgb* )srcImage.constScanLine( heightIndex );
62  for ( int widthIndex = 0; widthIndex < nCols; ++widthIndex )
63  {
64  px = scanLine[widthIndex];
65  int alpha = qAlpha( px );
66  alphaMatrix[pos] = alpha;
67  redMatrix[pos] = qRed( px );
68  greenMatrix[pos] = qGreen( px );
69  blueMatrix[pos] = qBlue( px );
70 
71  pos++;
72  }
73  }
74 
75  //derivative x
76  double* xDerivativeMatrixRed = new double[ nCols * nRows ];
77  xDerivativeMatrix( nCols, nRows, xDerivativeMatrixRed, redMatrix );
78  double* xDerivativeMatrixGreen = new double[ nCols * nRows ];
79  xDerivativeMatrix( nCols, nRows, xDerivativeMatrixGreen, greenMatrix );
80  double* xDerivativeMatrixBlue = new double[ nCols * nRows ];
81  xDerivativeMatrix( nCols, nRows, xDerivativeMatrixBlue, blueMatrix );
82  double* xDerivativeMatrixAlpha = new double[ nCols * nRows ];
83  xDerivativeMatrix( nCols, nRows, xDerivativeMatrixAlpha, alphaMatrix );
84 
85  //derivative y
86  double* yDerivativeMatrixRed = new double[ nCols * nRows ];
87  yDerivativeMatrix( nCols, nRows, yDerivativeMatrixRed, redMatrix );
88  double* yDerivativeMatrixGreen = new double[ nCols * nRows ];
89  yDerivativeMatrix( nCols, nRows, yDerivativeMatrixGreen, greenMatrix );
90  double* yDerivativeMatrixBlue = new double[ nCols * nRows ];
91  yDerivativeMatrix( nCols, nRows, yDerivativeMatrixBlue, blueMatrix );
92  double* yDerivativeMatrixAlpha = new double[ nCols * nRows ];
93  yDerivativeMatrix( nCols, nRows, yDerivativeMatrixAlpha, alphaMatrix );
94 
95  //compute output
96  double nSrcPerDstX = ( double ) srcImage.width() / ( double ) dstImage.width();
97  double nSrcPerDstY = ( double ) srcImage.height() / ( double ) dstImage.height();
98 
99  double currentSrcRow = nSrcPerDstY / 2.0 - 0.5;
100  double currentSrcCol;
101  int currentSrcColInt;
102  int currentSrcRowInt;
103  int lastSrcColInt = -100;
104  int lastSrcRowInt = -100;
105 
106  //bernstein polynomials
107  double bp0u, bp1u, bp2u, bp3u, bp0v, bp1v, bp2v, bp3v;
108  double u, v;
109 
110  for ( int y = 0; y < dstImage.height(); ++y )
111  {
112  currentSrcRowInt = floor( currentSrcRow );
113  v = currentSrcRow - currentSrcRowInt;
114 
115  currentSrcCol = nSrcPerDstX / 2.0 - 0.5;
116 
117  QRgb* scanLine = ( QRgb* )dstImage.scanLine( y );
118  for ( int x = 0; x < dstImage.width(); ++x )
119  {
120  currentSrcColInt = floor( currentSrcCol );
121  u = currentSrcCol - currentSrcColInt;
122 
123  //handle eight edge-cases
124  if (( currentSrcRowInt < 0 || currentSrcRowInt >= ( srcImage.height() - 1 ) || currentSrcColInt < 0 || currentSrcColInt >= ( srcImage.width() - 1 ) ) )
125  {
126  QRgb px1, px2;
127  //pixels at the border of the source image needs to be handled in a special way
128  if ( currentSrcRowInt < 0 && currentSrcColInt < 0 )
129  {
130  scanLine[x] = srcImage.pixel( 0, 0 );
131  }
132  else if ( currentSrcRowInt < 0 && currentSrcColInt >= ( srcImage.width() - 1 ) )
133  {
134  scanLine[x] = srcImage.pixel( srcImage.width() - 1, 0 );
135  }
136  else if ( currentSrcRowInt >= ( srcImage.height() - 1 ) && currentSrcColInt >= ( srcImage.width() - 1 ) )
137  {
138  scanLine[x] = srcImage.pixel( srcImage.width() - 1, srcImage.height() - 1 );
139  }
140  else if ( currentSrcRowInt >= ( srcImage.height() - 1 ) && currentSrcColInt < 0 )
141  {
142  scanLine[x] = srcImage.pixel( 0, srcImage.height() - 1 );
143  }
144  else if ( currentSrcRowInt < 0 )
145  {
146  px1 = srcImage.pixel( currentSrcColInt, 0 );
147  px2 = srcImage.pixel( currentSrcColInt + 1, 0 );
148  scanLine[x] = curveInterpolation( px1, px2, u, xDerivativeMatrixRed[ currentSrcColInt ], xDerivativeMatrixGreen[ currentSrcColInt ],
149  xDerivativeMatrixBlue[ currentSrcColInt ], xDerivativeMatrixAlpha[ currentSrcColInt ], xDerivativeMatrixRed[ currentSrcColInt + 1 ], xDerivativeMatrixGreen[ currentSrcColInt + 1 ],
150  xDerivativeMatrixBlue[ currentSrcColInt + 1 ], xDerivativeMatrixAlpha[ currentSrcColInt + 1 ] );
151  }
152  else if ( currentSrcRowInt >= ( srcImage.height() - 1 ) )
153  {
154  int idx = ( srcImage.height() - 1 ) * srcImage.width() + currentSrcColInt;
155  px1 = srcImage.pixel( currentSrcColInt, srcImage.height() - 1 );
156  px2 = srcImage.pixel( currentSrcColInt + 1, srcImage.height() - 1 );
157  scanLine[x] = curveInterpolation( px1, px2, u, xDerivativeMatrixRed[ idx ], xDerivativeMatrixGreen[ idx ], xDerivativeMatrixBlue[idx],
158  xDerivativeMatrixAlpha[idx], xDerivativeMatrixRed[ idx + 1 ], xDerivativeMatrixGreen[ idx + 1 ], xDerivativeMatrixBlue[idx + 1],
159  xDerivativeMatrixAlpha[idx + 1] );
160  }
161  else if ( currentSrcColInt < 0 )
162  {
163  int idx1 = currentSrcRowInt * srcImage.width();
164  int idx2 = idx1 + srcImage.width();
165  px1 = srcImage.pixel( 0, currentSrcRowInt );
166  px2 = srcImage.pixel( 0, currentSrcRowInt + 1 );
167  scanLine[x] = curveInterpolation( px1, px2, v, yDerivativeMatrixRed[ idx1 ], yDerivativeMatrixGreen[ idx1 ], yDerivativeMatrixBlue[ idx1],
168  yDerivativeMatrixAlpha[ idx1], yDerivativeMatrixRed[ idx2 ], yDerivativeMatrixGreen[ idx2 ], yDerivativeMatrixBlue[ idx2],
169  yDerivativeMatrixAlpha[ idx2] );
170  }
171  else if ( currentSrcColInt >= ( srcImage.width() - 1 ) )
172  {
173  int idx1 = currentSrcRowInt * srcImage.width() + srcImage.width() - 1;
174  int idx2 = idx1 + srcImage.width();
175  px1 = srcImage.pixel( srcImage.width() - 1, currentSrcRowInt );
176  px2 = srcImage.pixel( srcImage.width() - 1, currentSrcRowInt + 1 );
177  scanLine[x] = curveInterpolation( px1, px2, v, yDerivativeMatrixRed[ idx1 ], yDerivativeMatrixGreen[ idx1 ], yDerivativeMatrixBlue[ idx1],
178  yDerivativeMatrixAlpha[ idx1], yDerivativeMatrixRed[ idx2 ], yDerivativeMatrixGreen[ idx2 ], yDerivativeMatrixBlue[ idx2],
179  yDerivativeMatrixAlpha[ idx2] );
180  }
181  currentSrcCol += nSrcPerDstX;
182  continue;
183  }
184 
185  //first update the control points if necessary
186  if ( currentSrcColInt != lastSrcColInt || currentSrcRowInt != lastSrcRowInt )
187  {
188  calculateControlPoints( nCols, nRows, currentSrcRowInt, currentSrcColInt, redMatrix, greenMatrix, blueMatrix, alphaMatrix,
189  xDerivativeMatrixRed, xDerivativeMatrixGreen, xDerivativeMatrixBlue, xDerivativeMatrixAlpha,
190  yDerivativeMatrixRed, yDerivativeMatrixGreen, yDerivativeMatrixBlue, yDerivativeMatrixAlpha );
191  }
192 
193  //bernstein polynomials
194  bp0u = calcBernsteinPolyN3( 0, u ); bp1u = calcBernsteinPolyN3( 1, u );
195  bp2u = calcBernsteinPolyN3( 2, u ); bp3u = calcBernsteinPolyN3( 3, u );
196  bp0v = calcBernsteinPolyN3( 0, v ); bp1v = calcBernsteinPolyN3( 1, v );
197  bp2v = calcBernsteinPolyN3( 2, v ); bp3v = calcBernsteinPolyN3( 3, v );
198 
199  //then calculate value based on bernstein form of Bezier patch
200  //todo: move into function
201  int r = bp0u * bp0v * cRed00 +
202  bp1u * bp0v * cRed10 +
203  bp2u * bp0v * cRed20 +
204  bp3u * bp0v * cRed30 +
205  bp0u * bp1v * cRed01 +
206  bp1u * bp1v * cRed11 +
207  bp2u * bp1v * cRed21 +
208  bp3u * bp1v * cRed31 +
209  bp0u * bp2v * cRed02 +
210  bp1u * bp2v * cRed12 +
211  bp2u * bp2v * cRed22 +
212  bp3u * bp2v * cRed32 +
213  bp0u * bp3v * cRed03 +
214  bp1u * bp3v * cRed13 +
215  bp2u * bp3v * cRed23 +
216  bp3u * bp3v * cRed33;
217 
218  int g = bp0u * bp0v * cGreen00 +
219  bp1u * bp0v * cGreen10 +
220  bp2u * bp0v * cGreen20 +
221  bp3u * bp0v * cGreen30 +
222  bp0u * bp1v * cGreen01 +
223  bp1u * bp1v * cGreen11 +
224  bp2u * bp1v * cGreen21 +
225  bp3u * bp1v * cGreen31 +
226  bp0u * bp2v * cGreen02 +
227  bp1u * bp2v * cGreen12 +
228  bp2u * bp2v * cGreen22 +
229  bp3u * bp2v * cGreen32 +
230  bp0u * bp3v * cGreen03 +
231  bp1u * bp3v * cGreen13 +
232  bp2u * bp3v * cGreen23 +
233  bp3u * bp3v * cGreen33;
234 
235  int b = bp0u * bp0v * cBlue00 +
236  bp1u * bp0v * cBlue10 +
237  bp2u * bp0v * cBlue20 +
238  bp3u * bp0v * cBlue30 +
239  bp0u * bp1v * cBlue01 +
240  bp1u * bp1v * cBlue11 +
241  bp2u * bp1v * cBlue21 +
242  bp3u * bp1v * cBlue31 +
243  bp0u * bp2v * cBlue02 +
244  bp1u * bp2v * cBlue12 +
245  bp2u * bp2v * cBlue22 +
246  bp3u * bp2v * cBlue32 +
247  bp0u * bp3v * cBlue03 +
248  bp1u * bp3v * cBlue13 +
249  bp2u * bp3v * cBlue23 +
250  bp3u * bp3v * cBlue33;
251 
252  int a = bp0u * bp0v * cAlpha00 +
253  bp1u * bp0v * cAlpha10 +
254  bp2u * bp0v * cAlpha20 +
255  bp3u * bp0v * cAlpha30 +
256  bp0u * bp1v * cAlpha01 +
257  bp1u * bp1v * cAlpha11 +
258  bp2u * bp1v * cAlpha21 +
259  bp3u * bp1v * cAlpha31 +
260  bp0u * bp2v * cAlpha02 +
261  bp1u * bp2v * cAlpha12 +
262  bp2u * bp2v * cAlpha22 +
263  bp3u * bp2v * cAlpha32 +
264  bp0u * bp3v * cAlpha03 +
265  bp1u * bp3v * cAlpha13 +
266  bp2u * bp3v * cAlpha23 +
267  bp3u * bp3v * cAlpha33;
268 
269  scanLine[x] = createPremultipliedColor( r, g, b, a );
270 
271  lastSrcColInt = currentSrcColInt;
272  currentSrcCol += nSrcPerDstX;
273  }
274  lastSrcRowInt = currentSrcRowInt;
275  currentSrcRow += nSrcPerDstY;
276  }
277 
278 
279  //cleanup memory
280  delete[] redMatrix;
281  delete[] greenMatrix;
282  delete[] blueMatrix;
283  delete[] alphaMatrix;
284  delete[] xDerivativeMatrixRed;
285  delete[] xDerivativeMatrixGreen;
286  delete[] xDerivativeMatrixBlue;
287  delete[] xDerivativeMatrixAlpha;
288  delete[] yDerivativeMatrixRed;
289  delete[] yDerivativeMatrixGreen;
290  delete[] yDerivativeMatrixBlue;
291  delete[] yDerivativeMatrixAlpha;
292 }
293 
294 void QgsCubicRasterResampler::xDerivativeMatrix( int nCols, int nRows, double* matrix, const int* colorMatrix )
295 {
296  double val = 0;
297  int index = 0;
298 
299  for ( int y = 0; y < nRows; ++y )
300  {
301  for ( int x = 0; x < nCols; ++x )
302  {
303  if ( x == 0 )
304  {
305  val = colorMatrix[index + 1] - colorMatrix[index];
306  }
307  else if ( x == ( nCols - 1 ) )
308  {
309  val = colorMatrix[index] - colorMatrix[ index - 1 ];
310  }
311  else
312  {
313  val = ( colorMatrix[index + 1] - colorMatrix[index - 1] ) / 2.0;
314  }
315  matrix[index] = val;
316  ++index;
317  }
318  }
319 }
320 
321 void QgsCubicRasterResampler::yDerivativeMatrix( int nCols, int nRows, double* matrix, const int* colorMatrix )
322 {
323  double val = 0;
324  int index = 0;
325 
326  for ( int y = 0; y < nRows; ++y )
327  {
328  for ( int x = 0; x < nCols; ++x )
329  {
330  if ( y == 0 )
331  {
332  val = colorMatrix[ index + nCols ] - colorMatrix[ index ];
333  }
334  else if ( y == ( nRows - 1 ) )
335  {
336  val = colorMatrix[ index ] - colorMatrix[ index - nCols ];
337  }
338  else
339  {
340  val = ( colorMatrix[ index + nCols ] - colorMatrix[ index - nCols ] ) / 2.0;
341  }
342  matrix[index] = val;
343  ++index;
344  }
345  }
346 }
347 
348 void QgsCubicRasterResampler::calculateControlPoints( int nCols, int nRows, int currentRow, int currentCol, int* redMatrix, int* greenMatrix, int* blueMatrix,
349  int* alphaMatrix, double* xDerivativeMatrixRed, double* xDerivativeMatrixGreen, double* xDerivativeMatrixBlue, double* xDerivativeMatrixAlpha,
350  double* yDerivativeMatrixRed, double* yDerivativeMatrixGreen, double* yDerivativeMatrixBlue, double* yDerivativeMatrixAlpha )
351 {
352  Q_UNUSED( nRows );
353  int idx00 = currentRow * nCols + currentCol;
354  int idx10 = idx00 + 1;
355  int idx01 = idx00 + nCols;
356  int idx11 = idx01 + 1;
357 
358  //corner points
359  cRed00 = redMatrix[idx00]; cGreen00 = greenMatrix[idx00]; cBlue00 = blueMatrix[idx00]; cAlpha00 = alphaMatrix[idx00];
360  cRed30 = redMatrix[idx10]; cGreen30 = greenMatrix[idx10]; cBlue30 = blueMatrix[idx10]; cAlpha30 = alphaMatrix[idx10];
361  cRed03 = redMatrix[idx01]; cGreen03 = greenMatrix[idx01]; cBlue03 = blueMatrix[idx01]; cAlpha03 = alphaMatrix[idx01];
362  cRed33 = redMatrix[idx11]; cGreen33 = greenMatrix[idx11]; cBlue33 = blueMatrix[idx11]; cAlpha33 = alphaMatrix[idx11];
363 
364  //control points near c00
365  cRed10 = cRed00 + 0.333 * xDerivativeMatrixRed[idx00]; cGreen10 = cGreen00 + 0.333 * xDerivativeMatrixGreen[idx00];
366  cBlue10 = cBlue00 + 0.333 * xDerivativeMatrixBlue[idx00];cAlpha10 = cAlpha00 + 0.333 * xDerivativeMatrixAlpha[idx00];
367  cRed01 = cRed00 + 0.333 * yDerivativeMatrixRed[idx00]; cGreen01 = cGreen00 + 0.333 * yDerivativeMatrixGreen[idx00];
368  cBlue01 = cBlue00 + 0.333 * yDerivativeMatrixBlue[idx00];cAlpha01 = cAlpha00 + 0.333 * yDerivativeMatrixAlpha[idx00];
369  cRed11 = cRed10 + 0.333 * yDerivativeMatrixRed[idx00]; cGreen11 = cGreen10 + 0.333 * yDerivativeMatrixGreen[idx00];
370  cBlue11 = cBlue10 + 0.333 * yDerivativeMatrixBlue[idx00];cAlpha11 = cAlpha10 + 0.333 * yDerivativeMatrixAlpha[idx00];
371 
372  //control points near c30
373  cRed20 = cRed30 - 0.333 * xDerivativeMatrixRed[idx10]; cGreen20 = cGreen30 - 0.333 * xDerivativeMatrixGreen[idx10];
374  cBlue20 = cBlue30 - 0.333 * xDerivativeMatrixBlue[idx10]; cAlpha20 = cAlpha30 - 0.333 * xDerivativeMatrixAlpha[idx10];
375  cRed31 = cRed30 + 0.333 * yDerivativeMatrixRed[idx10]; cGreen31 = cGreen30 + 0.333 * yDerivativeMatrixGreen[idx10];
376  cBlue31 = cBlue30 + 0.333 * yDerivativeMatrixBlue[idx10]; cAlpha31 = cAlpha30 + 0.333 * yDerivativeMatrixAlpha[idx10];
377  cRed21 = cRed20 + 0.333 * yDerivativeMatrixRed[idx10]; cGreen21 = cGreen20 + 0.333 * yDerivativeMatrixGreen[idx10];
378  cBlue21 = cBlue20 + 0.333 * yDerivativeMatrixBlue[idx10]; cAlpha21 = cAlpha20 + 0.333 * yDerivativeMatrixAlpha[idx10];
379 
380  //control points near c03
381  cRed13 = cRed03 + 0.333 * xDerivativeMatrixRed[idx01]; cGreen13 = cGreen03 + 0.333 * xDerivativeMatrixGreen[idx01];
382  cBlue13 = cBlue03 + 0.333 * xDerivativeMatrixBlue[idx01]; cAlpha13 = cAlpha03 + 0.333 * xDerivativeMatrixAlpha[idx01];
383  cRed02 = cRed03 - 0.333 * yDerivativeMatrixRed[idx01]; cGreen02 = cGreen03 - 0.333 * yDerivativeMatrixGreen[idx01];
384  cBlue02 = cBlue03 - 0.333 * yDerivativeMatrixBlue[idx01]; cAlpha02 = cAlpha03 - 0.333 * yDerivativeMatrixAlpha[idx01];
385  cRed12 = cRed02 + 0.333 * xDerivativeMatrixRed[idx01]; cGreen12 = cGreen02 + 0.333 * xDerivativeMatrixGreen[idx01];
386  cBlue12 = cBlue02 + 0.333 * xDerivativeMatrixBlue[idx01]; cAlpha12 = cAlpha02 + 0.333 * xDerivativeMatrixAlpha[idx01];
387 
388  //control points near c33
389  cRed23 = cRed33 - 0.333 * xDerivativeMatrixRed[idx11]; cGreen23 = cGreen33 - 0.333 * xDerivativeMatrixGreen[idx11];
390  cBlue23 = cBlue33 - 0.333 * xDerivativeMatrixBlue[idx11]; cAlpha23 = cAlpha33 - 0.333 * xDerivativeMatrixAlpha[idx11];
391  cRed32 = cRed33 - 0.333 * yDerivativeMatrixRed[idx11]; cGreen32 = cGreen33 - 0.333 * yDerivativeMatrixGreen[idx11];
392  cBlue32 = cBlue33 - 0.333 * yDerivativeMatrixBlue[idx11]; cAlpha32 = cAlpha33 - 0.333 * yDerivativeMatrixAlpha[idx11];
393  cRed22 = cRed32 - 0.333 * xDerivativeMatrixRed[idx11]; cGreen22 = cGreen32 - 0.333 * xDerivativeMatrixGreen[idx11];
394  cBlue22 = cBlue32 - 0.333 * xDerivativeMatrixBlue[idx11]; cAlpha22 = cAlpha32 - 0.333 * xDerivativeMatrixAlpha[idx11];
395 }
396 
397 QRgb QgsCubicRasterResampler::curveInterpolation( QRgb pt1, QRgb pt2, double t, double d1red, double d1green, double d1blue, double d1alpha,
398  double d2red, double d2green, double d2blue, double d2alpha )
399 {
400  //control points
401  double p0r = qRed( pt1 ); double p1r = p0r + 0.333 * d1red; double p3r = qRed( pt2 ); double p2r = p3r - 0.333 * d2red;
402  double p0g = qGreen( pt1 ); double p1g = p0g + 0.333 * d1green; double p3g = qGreen( pt2 ); double p2g = p3g - 0.333 * d2green;
403  double p0b = qBlue( pt1 ); double p1b = p0b + 0.333 * d1blue; double p3b = qBlue( pt2 ); double p2b = p3b - 0.333 * d2blue;
404  double p0a = qAlpha( pt1 ); double p1a = p0a + 0.333 * d1alpha; double p3a = qAlpha( pt2 ); double p2a = p3a - 0.333 * d2alpha;
405 
406  //bernstein polynomials
407  double bp0 = calcBernsteinPolyN3( 0, t );
408  double bp1 = calcBernsteinPolyN3( 1, t );
409  double bp2 = calcBernsteinPolyN3( 2, t );
410  double bp3 = calcBernsteinPolyN3( 3, t );
411 
412  int red = bp0 * p0r + bp1 * p1r + bp2 * p2r + bp3 * p3r;
413  int green = bp0 * p0g + bp1 * p1g + bp2 * p2g + bp3 * p3g;
414  int blue = bp0 * p0b + bp1 * p1b + bp2 * p2b + bp3 * p3b;
415  int alpha = bp0 * p0a + bp1 * p1a + bp2 * p2a + bp3 * p3a;
416 
417  return createPremultipliedColor( red, green, blue, alpha );
418 }
419 
420 double QgsCubicRasterResampler::calcBernsteinPolyN3( int i, double t )
421 {
422  if ( i < 0 )
423  {
424  return 0;
425  }
426 
427  return lowerN3( i ) * qPow( t, i ) * qPow(( 1 - t ), ( 3 - i ) );
428 }
429 
430 inline int QgsCubicRasterResampler::lowerN3( int i )
431 {
432  switch ( i )
433  {
434  case 0:
435  case 3:
436  return 1;
437  case 1:
438  case 2:
439  return 3;
440  default:
441  return 0;
442  }
443 }
444 
445 QRgb QgsCubicRasterResampler::createPremultipliedColor( const int r, const int g, const int b, const int a )
446 {
447  int maxComponentBounds = qBound( 0, a, 255 );
448  return qRgba( qBound( 0, r, maxComponentBounds ),
449  qBound( 0, g, maxComponentBounds ),
450  qBound( 0, b, maxComponentBounds ),
451  a );
452 }
uchar * scanLine(int i)
static unsigned index
const uchar * constScanLine(int i) const
Interface for resampling rasters (e.g.
QgsRasterResampler * clone() const override
QRgb pixel(int x, int y) const
int width() const
void resample(const QImage &srcImage, QImage &dstImage) override
int height() const