AlbumShaper  1.0a3
Functions
contrast.h File Reference
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Functions

QImage * enhanceImageContrast (QString filename, StatusWidget *status)
 
void enhanceImageContrast (QImage *image, StatusWidget *status=NULL)
 

Function Documentation

§ enhanceImageContrast() [1/2]

QImage* enhanceImageContrast ( QString  filename,
StatusWidget status 
)

Definition at line 88 of file contrast.cpp.

References editedImage, and enhanceImageContrast().

Referenced by EdgeDetect::constructEdgeImage(), EditingInterface::enhanceContrast(), and enhanceImageContrast().

89 {
90  //load original image
91  QImage* editedImage = new QImage( filename );
92 
93  //convert to 32-bit depth if necessary
94  if( editedImage->depth() < 32 )
95  {
96  QImage* tmp = editedImage;
97  editedImage = new QImage( tmp->convertDepth( 32, Qt::AutoColor ) );
98  delete tmp; tmp=NULL;
99  }
100 
101  //enhance contrast
102  enhanceImageContrast( editedImage, status );
103 
104  //return pointer to edited image
105  return editedImage;
106 }
QImage * enhanceImageContrast(QString filename, StatusWidget *status)
Definition: contrast.cpp:88
QImage * editedImage

§ enhanceImageContrast() [2/2]

void enhanceImageContrast ( QImage *  image,
StatusWidget status = NULL 
)

Contrast stretching - http://www.ph.tn.tudelft.nl/Courses/FIP/frames/fip-istogram.html

Definition at line 108 of file contrast.cpp.

References b, HSVtoRGB(), StatusWidget::incrementProgress(), MAX, MIN, newProgress, RGBtoHSV(), RGBtoL(), StatusWidget::setStatus(), StatusWidget::showProgressBar(), and updateIncrement.

109 {
110  //setup progress bar
111  if(status)
112  {
113  QString statusMessage = qApp->translate( "enhanceImageContrast", "Enhancing Contrast:" );
114  status->showProgressBar( statusMessage, 100 );
115  qApp->processEvents();
116  }
117 
118  //update progress bar for every 1% of completion
119  const int updateIncrement = (int) ( 0.01 * editedImage->width() * editedImage->height() );
120  int newProgress = 0;
121 
125 
126  //construct intensity histograph
127  int grayVals[256];
128  int i=0;
129  for(i=0; i<256; i++) { grayVals[i] = 0; }
130 
131  //populate histogram by iterating over all image pixels
132  int numPixels = editedImage->width()*editedImage->height();
133  QRgb* rgb;
134  double grayValue;
135  uchar* scanLine;
136  int x, y;
137  for( y=0; y<editedImage->height(); y++)
138  {
139  //iterate over each selected pixel in scanline
140  scanLine = editedImage->scanLine(y);
141  for( x=0; x<editedImage->width(); x++)
142  {
143  rgb = ((QRgb*)scanLine+x);
144  grayValue = RGBtoL(rgb);
145  grayVals[(int)grayValue]++;
146  } //for x
147  } //for y
148 
149  //find 1% and 99% precenticles
150  //we'll stretch these values so we avoid outliers from affecting the stretch
151  int sum=0;
152  double indexLow, indexHigh;
153  indexLow = -1.0; indexHigh = -1.0;
154  for(i=0; i<256; i++)
155  {
156  sum+=grayVals[i];
157 
158  //if 1% not found yet and criteria met set index
159  if(indexLow < 0 &&
160  sum >= 0.01*numPixels)
161  {
162  indexLow = ((double)i)/255.0;
163  }
164 
165  //if 99% not found yet and criteria met set index
166  if(indexHigh < 0 &&
167  sum >= 0.99*numPixels)
168  {
169  indexHigh = ((double)i)/255.0;
170  }
171  }
172 
173  //only apply scaling if indexHigh > indexLow
174  if(indexHigh > indexLow)
175  {
176  //run through all image pixels a second time, this time scaling coordinates as necessary
177  for( y=0; y<editedImage->height(); y++)
178  {
179  //iterate over each selected pixel in scanline
180  scanLine = editedImage->scanLine(y);
181  for( x=0; x<editedImage->width(); x++)
182  {
183  //get color coordinates and convert to 0-1 scale
184  rgb = ((QRgb*)scanLine+x);
185  double r = ((double)qRed(*rgb) )/255.0;
186  double g = ((double)qGreen(*rgb) )/255.0;
187  double b = ((double)qBlue(*rgb) )/255.0;
188 
189  //convert to hsv
190  double h,s,v;
191  RGBtoHSV(r,g,b,&h,&s,&v);
192 
193  //scale and clamp v
194  v = (v-indexLow)/(indexHigh-indexLow);
195 
196  //convert adjusted color back to rgb colorspace and clamp
197  HSVtoRGB( &r,&g,&b, h,s,v);
198  int rp = (int) MIN( MAX((r*255), 0), 255 );
199  int gp = (int) MIN( MAX((g*255), 0), 255 );
200  int bp = (int) MIN( MAX((b*255), 0), 255 );
201 
202  //set adjusted color value
203  *rgb = qRgb(rp,gp,bp);
204 
205  //update status bar if significant progress has been made since last update
206  if(status)
207  {
208  newProgress++;
209  if(newProgress >= updateIncrement)
210  {
211  newProgress = 0;
212  status->incrementProgress();
213  qApp->processEvents();
214  }
215  }
216 
217  } //for x
218  } //for y
219  } //if scaling should be preforemd
220 
221  //remove status bar
222  if(status)
223  {
224  status->setStatus( "" );
225  qApp->processEvents();
226  }
227 }
int updateIncrement
double RGBtoL(QRgb *rgb)
find luminance of a rgb color triplet
Definition: imageTools.cpp:217
void HSVtoRGB(double *r, double *g, double *b, double h, double s, double v)
Convert a HSV color triplet to RGB.
Definition: imageTools.cpp:264
void incrementProgress()
Updates the progress bar by one step.
void showProgressBar(QString message, int numSteps)
Initializes the progress bar.
long b
Definition: jpegInternal.h:125
void setStatus(QString message)
Update message.
#define MIN(x, y)
Definition: contrast.cpp:21
void RGBtoHSV(double r, double g, double b, double *h, double *s, double *v)
Convert a RGB color triplet to HSV.
Definition: imageTools.cpp:231
#define MAX(x, y)
Definition: contrast.cpp:22
QImage * editedImage
int newProgress