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<h1>color.cpp</h1><a href="color_8cpp.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">//==============================================</span>
<a name="l00002"></a>00002 <span class="comment">// copyright : (C) 2003-2005 by Will Stokes</span>
<a name="l00003"></a>00003 <span class="comment">//==============================================</span>
<a name="l00004"></a>00004 <span class="comment">// This program is free software; you can redistribute it</span>
<a name="l00005"></a>00005 <span class="comment">// and/or modify it under the terms of the GNU General</span>
<a name="l00006"></a>00006 <span class="comment">// Public License as published by the Free Software</span>
<a name="l00007"></a>00007 <span class="comment">// Foundation; either version 2 of the License, or</span>
<a name="l00008"></a>00008 <span class="comment">// (at your option) any later version.</span>
<a name="l00009"></a>00009 <span class="comment">//==============================================</span>
<a name="l00010"></a>00010
<a name="l00011"></a>00011 <span class="comment">//Systemwide includes</span>
<a name="l00012"></a>00012 <span class="preprocessor">#include <qimage.h></span>
<a name="l00013"></a>00013 <span class="preprocessor">#include <qstring.h></span>
<a name="l00014"></a>00014 <span class="preprocessor">#include <qapplication.h></span>
<a name="l00015"></a>00015
<a name="l00016"></a>00016 <span class="comment">//Projectwide includes</span>
<a name="l00017"></a>00017 <span class="preprocessor">#include "<a class="code" href="color_8h.html">color.h</a>"</span>
<a name="l00018"></a>00018 <span class="preprocessor">#include "../../gui/statusWidget.h"</span>
<a name="l00019"></a>00019
<a name="l00020"></a>00020 <span class="comment">//----------------------------------------------</span>
<a name="l00021"></a>00021 <span class="comment">// Inputs:</span>
<a name="l00022"></a>00022 <span class="comment">// -------</span>
<a name="l00023"></a>00023 <span class="comment">// QString filename - location of original image on disk</span>
<a name="l00024"></a>00024 <span class="comment">// StatusWidget* status - widget for making progress visible to user</span>
<a name="l00025"></a>00025 <span class="comment">//</span>
<a name="l00026"></a>00026 <span class="comment">// Outputs:</span>
<a name="l00027"></a>00027 <span class="comment">// --------</span>
<a name="l00028"></a>00028 <span class="comment">// QImage* returned - constructed image</span>
<a name="l00029"></a>00029 <span class="comment">//</span>
<a name="l00030"></a>00030 <span class="comment">// Description:</span>
<a name="l00031"></a>00031 <span class="comment">// ------------</span>
<a name="l00032"></a>00032 <span class="comment">// This method simply stretchs the color values to use up the entire dynamic range, in our</span>
<a name="l00033"></a>00033 <span class="comment">// case red/green/blue values ranging from [0,255].</span>
<a name="l00034"></a>00034 <span class="comment">//</span>
<a name="l00035"></a>00035 <span class="comment">// The algorithm can be broken up into two steps:</span>
<a name="l00036"></a>00036 <span class="comment">// 1.) finding the endpoints of the curretn color values (e.g. [6,120])</span>
<a name="l00037"></a>00037 <span class="comment">// 2.) stretching the current image colors to fit the full [0,255] range</span>
<a name="l00038"></a>00038 <span class="comment">//</span>
<a name="l00039"></a>00039 <span class="comment">// One could simply iterate over the entire image and find the minimum and </span>
<a name="l00040"></a>00040 <span class="comment">// maximum red, gree, and blue color values. However; often there is residual </span>
<a name="l00041"></a>00041 <span class="comment">// noise at the endpoints since camera sensors always provide some noise, </span>
<a name="l00042"></a>00042 <span class="comment">// while the majority of pixels fall somewhere in the middle. If we constructed </span>
<a name="l00043"></a>00043 <span class="comment">// a histogram for a particular color channel it might look like this:</span>
<a name="l00044"></a>00044 <span class="comment">// 5 | .</span>
<a name="l00045"></a>00045 <span class="comment">// . | . .</span>
<a name="l00046"></a>00046 <span class="comment">// . | . .</span>
<a name="l00047"></a>00047 <span class="comment">// 1 | . . . . .</span>
<a name="l00048"></a>00048 <span class="comment">// 0 |. .... ........ ............. .....</span>
<a name="l00049"></a>00049 <span class="comment">// |-X------------*--------------*-----------X-----</span>
<a name="l00050"></a>00050 <span class="comment">// 0 100 175 255 </span>
<a name="l00051"></a>00051 <span class="comment">//</span>
<a name="l00052"></a>00052 <span class="comment">//</span>
<a name="l00053"></a>00053 <span class="comment">// Here color values are plotted across the x axis, while the y axis indicates </span>
<a name="l00054"></a>00054 <span class="comment">// how offten a particular color value was seen. Note we're plotting one of the </span>
<a name="l00055"></a>00055 <span class="comment">// three color channels here (red, green, blue).</span>
<a name="l00056"></a>00056 <span class="comment">//</span>
<a name="l00057"></a>00057 <span class="comment">// In this example we notice most pixels that were observed fall in the 100-175 </span>
<a name="l00058"></a>00058 <span class="comment">// range (that is the red/green/blue color value was most often observed with a </span>
<a name="l00059"></a>00059 <span class="comment">// value between 100-175). A few pixels with values of 5 or 10 were seen, and a </span>
<a name="l00060"></a>00060 <span class="comment">// few with around 230 were seen. We want to stretch the common case, 100-175, </span>
<a name="l00061"></a>00061 <span class="comment">// out to the full 0-255 range. That will make the pixels that were 175 now 255, </span>
<a name="l00062"></a>00062 <span class="comment">// those that wer 100 now 0, thus darks will become darker, brights will become</span>
<a name="l00063"></a>00063 <span class="comment">// brigther. We'll lineraly scale all pixels inbetween. Any pixels beyond the </span>
<a name="l00064"></a>00064 <span class="comment">// 100-175 range will get clamped at 0 and 255 respectively.</span>
<a name="l00065"></a>00065 <span class="comment">//</span>
<a name="l00066"></a>00066 <span class="comment">// Now, if we simply find the smallest and largest values we'll get soemthinglike </span>
<a name="l00067"></a>00067 <span class="comment">// 5 and 235, and stretching will have very little effect on the image. Instead, </span>
<a name="l00068"></a>00068 <span class="comment">// we first actually populate a histogram array for each color channel (an int </span>
<a name="l00069"></a>00069 <span class="comment">// array of 256 elements). We then determine the 1% and 99% boundaries but walking </span>
<a name="l00070"></a>00070 <span class="comment">// from the end points of hte histogram array and adding up the elements. Once 1% </span>
<a name="l00071"></a>00071 <span class="comment">// of the pixels have been accounted for we set the the boundary endpoint to the index, </span>
<a name="l00072"></a>00072 <span class="comment">// thus giving us 100,175 in this case.</span>
<a name="l00073"></a>00073 <span class="comment">//</span>
<a name="l00074"></a>00074 <span class="comment">// Actually scaling the colors is relatively trivial. A second pass over the </span>
<a name="l00075"></a>00075 <span class="comment">// image takes place during which a pixels color is fetched, modified, then written </span>
<a name="l00076"></a>00076 <span class="comment">// back out according to the following equations. It should be noted that as a </span>
<a name="l00077"></a>00077 <span class="comment">// sanity check we clamp scaled color values to the [0,255] range.</span>
<a name="l00078"></a>00078 <span class="comment">//</span>
<a name="l00079"></a>00079 <span class="comment">// r' = [255*(r-rLow)] / [rHigh - rLow]</span>
<a name="l00080"></a>00080 <span class="comment">// g' = [255*(g-gLow)] / [gHigh - gLow]</span>
<a name="l00081"></a>00081 <span class="comment">// b' = [255*(b-bLow)] / [bHigh - bLow]</span>
<a name="l00082"></a>00082 <span class="comment">//</span>
<a name="l00083"></a>00083 <span class="comment">// where [r/g/b][Low/High] refer to the 1% and 99% endpoints for the red, </span>
<a name="l00084"></a>00084 <span class="comment">// green, and blue color changes respectively.</span>
<a name="l00085"></a>00085 <span class="comment">//</span>
<a name="l00086"></a>00086 <span class="comment">//----------------------------------------------</span>
<a name="l00087"></a>00087
<a name="l00088"></a>00088 <span class="comment">//==============================================</span>
<a name="l00089"></a><a class="code" href="color_8h.html#e7c58c9889965ef85e26584ebdabef3c">00089</a> QImage* <a class="code" href="color_8cpp.html#e7c58c9889965ef85e26584ebdabef3c">improveColorBalance</a>( QString filename, <a class="code" href="classStatusWidget.html">StatusWidget</a>* <a class="code" href="redEye__internal_8h.html#65b682074aef9e63bb1dad48c3e9e9df">status</a> )
<a name="l00090"></a>00090 {
<a name="l00091"></a>00091 <span class="comment">//load original image</span>
<a name="l00092"></a>00092 QImage* <a class="code" href="redEye__internal_8h.html#63116a8b94b4ed0e99ddcb7f6f3bd919">editedImage</a> = <span class="keyword">new</span> QImage( filename );
<a name="l00093"></a>00093
<a name="l00094"></a>00094 <span class="comment">//convert to 32-bit depth if necessary</span>
<a name="l00095"></a>00095 <span class="keywordflow">if</span>( editedImage->depth() < 32 )
<a name="l00096"></a>00096 {
<a name="l00097"></a>00097 QImage* tmp = editedImage;
<a name="l00098"></a>00098 editedImage = <span class="keyword">new</span> QImage( tmp->convertDepth( 32, Qt::AutoColor ) );
<a name="l00099"></a>00099 <span class="keyword">delete</span> tmp; tmp=NULL;
<a name="l00100"></a>00100 }
<a name="l00101"></a>00101
<a name="l00102"></a>00102 <span class="comment">//setup progress bar</span>
<a name="l00103"></a>00103 QString statusMessage = qApp->translate( <span class="stringliteral">"improveColorBalance"</span>, <span class="stringliteral">"Enhancing Color Balance:"</span> );
<a name="l00104"></a>00104 status-><a class="code" href="classStatusWidget.html#57d461014070b9d651c36bd157cab9c1" title="Initializes the progress bar.">showProgressBar</a>( statusMessage, 100 );
<a name="l00105"></a>00105 qApp->processEvents();
<a name="l00106"></a>00106
<a name="l00107"></a>00107 <span class="comment">//update progress bar for every 1% of completion</span>
<a name="l00108"></a>00108 <span class="keyword">const</span> <span class="keywordtype">int</span> <a class="code" href="redEye__internal_8h.html#32598f506d413f48cda8e1c930dae6b3">updateIncrement</a> = (int) ( 0.01 * editedImage->width() * editedImage->height() );
<a name="l00109"></a>00109 <span class="keywordtype">int</span> <a class="code" href="redEye__internal_8h.html#caa08422437cae250a76ca488cbe1567">newProgress</a> = 0;
<a name="l00110"></a>00110
<a name="l00111"></a>00111 <span class="comment">//construct intensity histographs for each color channel</span>
<a name="l00112"></a>00112 <span class="keywordtype">int</span> redVals[256];
<a name="l00113"></a>00113 <span class="keywordtype">int</span> greenVals[256];
<a name="l00114"></a>00114 <span class="keywordtype">int</span> blueVals[256];
<a name="l00115"></a>00115 <span class="keywordtype">int</span> i=0;
<a name="l00116"></a>00116 <span class="keywordflow">for</span>(i=0; i<256; i++)
<a name="l00117"></a>00117 {
<a name="l00118"></a>00118 redVals[i] = 0;
<a name="l00119"></a>00119 greenVals[i] = 0;
<a name="l00120"></a>00120 blueVals[i] = 0;
<a name="l00121"></a>00121 }
<a name="l00122"></a>00122
<a name="l00123"></a>00123 <span class="comment">//populate histogram by iterating over all image pixels</span>
<a name="l00124"></a>00124 <span class="keywordtype">int</span> numPixels = editedImage->width()*editedImage->height();
<a name="l00125"></a>00125 QRgb* rgb;
<a name="l00126"></a>00126 uchar* scanLine;
<a name="l00127"></a>00127 <span class="keywordtype">int</span> x, y;
<a name="l00128"></a>00128 <span class="keywordflow">for</span>( y=0; y<editedImage->height(); y++)
<a name="l00129"></a>00129 {
<a name="l00130"></a>00130 <span class="comment">//iterate over each selected pixel in scanline</span>
<a name="l00131"></a>00131 scanLine = editedImage->scanLine(y);
<a name="l00132"></a>00132 <span class="keywordflow">for</span>( x=0; x<editedImage->width(); x++)
<a name="l00133"></a>00133 {
<a name="l00134"></a>00134 rgb = ((QRgb*)scanLine+x);
<a name="l00135"></a>00135 redVals[qRed(*rgb)]++;
<a name="l00136"></a>00136 greenVals[qGreen(*rgb)]++;
<a name="l00137"></a>00137 blueVals[qBlue(*rgb)]++;
<a name="l00138"></a>00138 } <span class="comment">//for x</span>
<a name="l00139"></a>00139 } <span class="comment">//for y</span>
<a name="l00140"></a>00140
<a name="l00141"></a>00141 <span class="comment">//find 1% and 99% precenticles</span>
<a name="l00142"></a>00142 <span class="comment">//we'll stretch these values so we avoid outliers from affecting the stretch</span>
<a name="l00143"></a>00143 <span class="keywordtype">int</span> sumR=0;
<a name="l00144"></a>00144 <span class="keywordtype">int</span> sumG=0;
<a name="l00145"></a>00145 <span class="keywordtype">int</span> sumB=0;
<a name="l00146"></a>00146 <span class="keywordtype">int</span> indexLowR, indexHighR;
<a name="l00147"></a>00147 <span class="keywordtype">int</span> indexLowG, indexHighG;
<a name="l00148"></a>00148 <span class="keywordtype">int</span> indexLowB, indexHighB;
<a name="l00149"></a>00149 indexLowR = -1; indexHighR = -1;
<a name="l00150"></a>00150 indexLowG = -1; indexHighG = -1;
<a name="l00151"></a>00151 indexLowB = -1; indexHighB = -1;
<a name="l00152"></a>00152 <span class="keywordflow">for</span>(i=0; i<256; i++)
<a name="l00153"></a>00153 {
<a name="l00154"></a>00154 sumR+=redVals[i];
<a name="l00155"></a>00155 sumG+=greenVals[i];
<a name="l00156"></a>00156 sumB+=blueVals[i];
<a name="l00157"></a>00157
<a name="l00158"></a>00158 <span class="comment">//if 1% not found yet and criteria met set index</span>
<a name="l00159"></a>00159 <span class="keywordflow">if</span>(indexLowR < 0 && sumR >= 0.01*numPixels)
<a name="l00160"></a>00160 { indexLowR = i; }
<a name="l00161"></a>00161 <span class="keywordflow">if</span>(indexLowG < 0 && sumG >= 0.01*numPixels)
<a name="l00162"></a>00162 { indexLowG = i; }
<a name="l00163"></a>00163 <span class="keywordflow">if</span>(indexLowB < 0 && sumB >= 0.01*numPixels)
<a name="l00164"></a>00164 { indexLowB = i; }
<a name="l00165"></a>00165
<a name="l00166"></a>00166 <span class="comment">//if 99% not found yet and criteria met set index</span>
<a name="l00167"></a>00167 <span class="keywordflow">if</span>(indexHighR < 0 && sumR >= 0.99*numPixels)
<a name="l00168"></a>00168 { indexHighR = i; }
<a name="l00169"></a>00169 <span class="keywordflow">if</span>(indexHighG < 0 && sumG >= 0.99*numPixels)
<a name="l00170"></a>00170 { indexHighG = i; }
<a name="l00171"></a>00171 <span class="keywordflow">if</span>(indexHighB < 0 && sumB >= 0.99*numPixels)
<a name="l00172"></a>00172 { indexHighB = i; }
<a name="l00173"></a>00173 }
<a name="l00174"></a>00174
<a name="l00175"></a>00175 <span class="comment">//run through all image pixels a second time, this time scaling coordinates as necessary</span>
<a name="l00176"></a>00176 <span class="keywordflow">for</span>( y=0; y<editedImage->height(); y++)
<a name="l00177"></a>00177 {
<a name="l00178"></a>00178 <span class="comment">//iterate over each selected pixel in scanline</span>
<a name="l00179"></a>00179 scanLine = editedImage->scanLine(y);
<a name="l00180"></a>00180 <span class="keywordflow">for</span>( x=0; x<editedImage->width(); x++)
<a name="l00181"></a>00181 {
<a name="l00182"></a>00182 <span class="comment">//get color coordinates and convert to 0-1 scale</span>
<a name="l00183"></a>00183 rgb = ((QRgb*)scanLine+x);
<a name="l00184"></a>00184 <span class="keywordtype">double</span> r = ((double)qRed(*rgb) );
<a name="l00185"></a>00185 <span class="keywordtype">double</span> g = ((double)qGreen(*rgb) );
<a name="l00186"></a>00186 <span class="keywordtype">double</span> <a class="code" href="jpegInternal_8h.html#f320905358fa78701e4cc60b6135601f">b</a> = ((double)qBlue(*rgb) );
<a name="l00187"></a>00187
<a name="l00188"></a>00188 <span class="keywordflow">if</span>(indexHighR != indexLowR) { r = (255*(r-indexLowR))/(indexHighR-indexLowR); }
<a name="l00189"></a>00189 <span class="keywordflow">if</span>(indexHighG != indexLowG) { g = (255*(g-indexLowG))/(indexHighG-indexLowG); }
<a name="l00190"></a>00190 <span class="keywordflow">if</span>(indexHighB != indexLowB) { b = (255*(b-indexLowB))/(indexHighB-indexLowB); }
<a name="l00191"></a>00191
<a name="l00192"></a>00192 <span class="keywordtype">int</span> rp = (int) QMIN( QMAX(r, 0), 255 );
<a name="l00193"></a>00193 <span class="keywordtype">int</span> gp = (int) QMIN( QMAX(g, 0), 255 );
<a name="l00194"></a>00194 <span class="keywordtype">int</span> bp = (int) QMIN( QMAX(b, 0), 255 );
<a name="l00195"></a>00195
<a name="l00196"></a>00196 <span class="comment">//set adjusted color value</span>
<a name="l00197"></a>00197 *rgb = qRgb(rp,gp,bp);
<a name="l00198"></a>00198
<a name="l00199"></a>00199 <span class="comment">//update status bar if significant progress has been made since last update</span>
<a name="l00200"></a>00200 newProgress++;
<a name="l00201"></a>00201 <span class="keywordflow">if</span>(newProgress >= updateIncrement)
<a name="l00202"></a>00202 {
<a name="l00203"></a>00203 newProgress = 0;
<a name="l00204"></a>00204 status-><a class="code" href="classStatusWidget.html#de18735223ae40506c32c96b9c9c5476" title="Updates the progress bar by one step.">incrementProgress</a>();
<a name="l00205"></a>00205 qApp->processEvents();
<a name="l00206"></a>00206 }
<a name="l00207"></a>00207
<a name="l00208"></a>00208 } <span class="comment">//for x</span>
<a name="l00209"></a>00209 } <span class="comment">//for y</span>
<a name="l00210"></a>00210
<a name="l00211"></a>00211 <span class="comment">//remove status bar</span>
<a name="l00212"></a>00212 status-><a class="code" href="classStatusWidget.html#02084869ff1c15dab4bc922a49b31808" title="Update message.">setStatus</a>( <span class="stringliteral">""</span> );
<a name="l00213"></a>00213 qApp->processEvents();
<a name="l00214"></a>00214
<a name="l00215"></a>00215 <span class="comment">//return pointer to edited image</span>
<a name="l00216"></a>00216 <span class="keywordflow">return</span> editedImage;
<a name="l00217"></a>00217 }
<a name="l00218"></a>00218 <span class="comment">//==============================================</span>
</pre></div></div>
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