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<h1>contrast.cpp</h1><a href="contrast_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="contrast_8h.html">contrast.h</a>"</span>
<a name="l00018"></a>00018 <span class="preprocessor">#include "../tools/imageTools.h"</span>
<a name="l00019"></a>00019 <span class="preprocessor">#include "../../gui/statusWidget.h"</span>
<a name="l00020"></a>00020
<a name="l00021"></a>00021 <span class="comment">//----------------------------------------------</span>
<a name="l00022"></a>00022 <span class="comment">// Inputs:</span>
<a name="l00023"></a>00023 <span class="comment">// -------</span>
<a name="l00024"></a>00024 <span class="comment">// QString filename - location of original image on disk</span>
<a name="l00025"></a>00025 <span class="comment">// StatusWidget* status - widget for making progress visible to user</span>
<a name="l00026"></a>00026 <span class="comment">//</span>
<a name="l00027"></a>00027 <span class="comment">// Outputs:</span>
<a name="l00028"></a>00028 <span class="comment">// --------</span>
<a name="l00029"></a>00029 <span class="comment">// QImage* returned - constructed image</span>
<a name="l00030"></a>00030 <span class="comment">//</span>
<a name="l00031"></a>00031 <span class="comment">// Description:</span>
<a name="l00032"></a>00032 <span class="comment">// ------------</span>
<a name="l00033"></a>00033 <span class="comment">// This method simply stretchs the luminance rnage to use up the entire dynamic range, in our</span>
<a name="l00034"></a>00034 <span class="comment">// case from [0,255]. This algorithm is very similar to the color enhancement algorithm, except</span>
<a name="l00035"></a>00035 <span class="comment">// in this case we convert color values to HSL space and work with the L values (luminance).</span>
<a name="l00036"></a>00036 <span class="comment">//</span>
<a name="l00037"></a>00037 <span class="comment">// The algorithm can be broken up into two steps:</span>
<a name="l00038"></a>00038 <span class="comment">// 1.) finding the current luminance endpoints (e.g. [6,120])</span>
<a name="l00039"></a>00039 <span class="comment">// 2.) stretching the luminance range to fit the full [0,255] range</span>
<a name="l00040"></a>00040 <span class="comment">//</span>
<a name="l00041"></a>00041 <span class="comment">// One could simply iterate over the entire image and find the minimum and </span>
<a name="l00042"></a>00042 <span class="comment">// maximum luminance values. However; often there is residual </span>
<a name="l00043"></a>00043 <span class="comment">// noise at the endpoints since camera sensors always provide some noise, </span>
<a name="l00044"></a>00044 <span class="comment">// while the majority of pixels fall somewhere in the middle. If we constructed </span>
<a name="l00045"></a>00045 <span class="comment">// a histogram for of pixel luminance values it might look like this:</span>
<a name="l00046"></a>00046 <span class="comment">// 5 | .</span>
<a name="l00047"></a>00047 <span class="comment">// . | . .</span>
<a name="l00048"></a>00048 <span class="comment">// . | . .</span>
<a name="l00049"></a>00049 <span class="comment">// 1 | . . . . .</span>
<a name="l00050"></a>00050 <span class="comment">// 0 |. .... ........ ............. .....</span>
<a name="l00051"></a>00051 <span class="comment">// |-X------------*--------------*-----------X-----</span>
<a name="l00052"></a>00052 <span class="comment">// 0 100 175 255 </span>
<a name="l00053"></a>00053 <span class="comment">//</span>
<a name="l00054"></a>00054 <span class="comment">// Here luminance values are plotted across the x axis, while the y axis indicates </span>
<a name="l00055"></a>00055 <span class="comment">// how offten a particular luminance value was seen.</span>
<a name="l00056"></a>00056 <span class="comment">//</span>
<a name="l00057"></a>00057 <span class="comment">// In this example we notice most pixel luminance values were observed fall in </span>
<a name="l00058"></a>00058 <span class="comment">// the 100-175 range. A few pixels with values of 5 or 10 were seen, and a </span>
<a name="l00059"></a>00059 <span class="comment">// few with around 230 were seen. We want to stretch the common case, 100-175, </span>
<a name="l00060"></a>00060 <span class="comment">// out to the full 0-255 range. That will make the pixels that were 175 now 255, </span>
<a name="l00061"></a>00061 <span class="comment">// those that wer 100 now 0, thus darks will become darker, brights will become</span>
<a name="l00062"></a>00062 <span class="comment">// brigther. We'll lineraly scale all pixels inbetween. Any pixels beyond the </span>
<a name="l00063"></a>00063 <span class="comment">// 100-175 range will get clamped at 0 and 255 respectively.</span>
<a name="l00064"></a>00064 <span class="comment">//</span>
<a name="l00065"></a>00065 <span class="comment">// Now, if we simply find the smallest and largest values we'll get soemthinglike </span>
<a name="l00066"></a>00066 <span class="comment">// 5 and 235, and stretching will have very little effect on the image. Instead, </span>
<a name="l00067"></a>00067 <span class="comment">// we first actually populate a histogram array, then determine the 1% and </span>
<a name="l00068"></a>00068 <span class="comment">// 99% boundaries but walking from the end points of hte histogram array and </span>
<a name="l00069"></a>00069 <span class="comment">// adding up the elements. Once 1% of the pixels have been accounted for we set </span>
<a name="l00070"></a>00070 <span class="comment">// the boundary endpoint to the current index, thus giving us 100,175 in this case.</span>
<a name="l00071"></a>00071 <span class="comment">//</span>
<a name="l00072"></a>00072 <span class="comment">// Scaling the pixels is only marginally more complicated when in </span>
<a name="l00073"></a>00073 <span class="comment">// the color enhancement algorithm. A second pass over the </span>
<a name="l00074"></a>00074 <span class="comment">// image takes place during which a pixels color is fetched, converted to HSL,</span>
<a name="l00075"></a>00075 <span class="comment">// the luminance is stretched according to the following equation, the color is</span>
<a name="l00076"></a>00076 <span class="comment">// converted back to RGB, and the value is written back to the image.</span>
<a name="l00077"></a>00077 <span class="comment">//</span>
<a name="l00078"></a>00078 <span class="comment">// l' = [255*(l-lLow)] / [lHigh - lLow]</span>
<a name="l00079"></a>00079 <span class="comment">//</span>
<a name="l00080"></a>00080 <span class="comment">// where l[Low/High] refer to the 1% and 99% endpoints for the luminance histogram.</span>
<a name="l00081"></a>00081 <span class="comment">//</span>
<a name="l00082"></a>00082 <span class="comment">//----------------------------------------------</span>
<a name="l00083"></a>00083
<a name="l00084"></a>00084 <span class="comment">//==============================================</span>
<a name="l00085"></a><a class="code" href="contrast_8h.html#5a7a57ce540b35b0987153951f45a398">00085</a> QImage* <a class="code" href="contrast_8cpp.html#5a7a57ce540b35b0987153951f45a398">enhanceImageContrast</a>( QString filename, <a class="code" href="classStatusWidget.html">StatusWidget</a>* <a class="code" href="redEye__internal_8h.html#65b682074aef9e63bb1dad48c3e9e9df">status</a> )
<a name="l00086"></a>00086 {
<a name="l00087"></a>00087 <span class="comment">//load original image</span>
<a name="l00088"></a>00088 QImage* <a class="code" href="redEye__internal_8h.html#63116a8b94b4ed0e99ddcb7f6f3bd919">editedImage</a> = <span class="keyword">new</span> QImage( filename );
<a name="l00089"></a>00089
<a name="l00090"></a>00090 <span class="comment">//convert to 32-bit depth if necessary</span>
<a name="l00091"></a>00091 <span class="keywordflow">if</span>( editedImage->depth() < 32 )
<a name="l00092"></a>00092 {
<a name="l00093"></a>00093 QImage* tmp = editedImage;
<a name="l00094"></a>00094 editedImage = <span class="keyword">new</span> QImage( tmp->convertDepth( 32, Qt::AutoColor ) );
<a name="l00095"></a>00095 <span class="keyword">delete</span> tmp; tmp=NULL;
<a name="l00096"></a>00096 }
<a name="l00097"></a>00097
<a name="l00098"></a>00098 <span class="comment">//enhance contrast</span>
<a name="l00099"></a>00099 <a class="code" href="contrast_8cpp.html#5a7a57ce540b35b0987153951f45a398">enhanceImageContrast</a>( editedImage, status );
<a name="l00100"></a>00100
<a name="l00101"></a>00101 <span class="comment">//return pointer to edited image</span>
<a name="l00102"></a>00102 <span class="keywordflow">return</span> editedImage;
<a name="l00103"></a>00103 }
<a name="l00104"></a>00104 <span class="comment">//==============================================</span>
<a name="l00105"></a><a class="code" href="contrast_8h.html#00f1d7b1aeff3381f41fa67e0f8a334b">00105</a> <span class="keywordtype">void</span> <a class="code" href="contrast_8cpp.html#5a7a57ce540b35b0987153951f45a398">enhanceImageContrast</a>( QImage* <a class="code" href="redEye__internal_8h.html#63116a8b94b4ed0e99ddcb7f6f3bd919">editedImage</a>, <a class="code" href="classStatusWidget.html">StatusWidget</a>* <a class="code" href="redEye__internal_8h.html#65b682074aef9e63bb1dad48c3e9e9df">status</a> )
<a name="l00106"></a>00106 {
<a name="l00107"></a>00107 <span class="comment">//setup progress bar</span>
<a name="l00108"></a>00108 <span class="keywordflow">if</span>(status)
<a name="l00109"></a>00109 {
<a name="l00110"></a>00110 QString statusMessage = qApp->translate( <span class="stringliteral">"enhanceImageContrast"</span>, <span class="stringliteral">"Enhancing Contrast:"</span> );
<a name="l00111"></a>00111 status-><a class="code" href="classStatusWidget.html#57d461014070b9d651c36bd157cab9c1" title="Initializes the progress bar.">showProgressBar</a>( statusMessage, 100 );
<a name="l00112"></a>00112 qApp->processEvents();
<a name="l00113"></a>00113 }
<a name="l00114"></a>00114
<a name="l00115"></a>00115 <span class="comment">//update progress bar for every 1% of completion</span>
<a name="l00116"></a>00116 <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="l00117"></a>00117 <span class="keywordtype">int</span> <a class="code" href="redEye__internal_8h.html#caa08422437cae250a76ca488cbe1567">newProgress</a> = 0;
<a name="l00118"></a>00118
<a name="l00122"></a>00122
<a name="l00123"></a>00123 <span class="comment">//construct intensity histograph</span>
<a name="l00124"></a>00124 <span class="keywordtype">int</span> grayVals[256];
<a name="l00125"></a>00125 <span class="keywordtype">int</span> i=0;
<a name="l00126"></a>00126 <span class="keywordflow">for</span>(i=0; i<256; i++) { grayVals[i] = 0; }
<a name="l00127"></a>00127
<a name="l00128"></a>00128 <span class="comment">//populate histogram by iterating over all image pixels</span>
<a name="l00129"></a>00129 <span class="keywordtype">int</span> numPixels = editedImage->width()*editedImage->height();
<a name="l00130"></a>00130 QRgb* rgb;
<a name="l00131"></a>00131 <span class="keywordtype">double</span> grayValue;
<a name="l00132"></a>00132 uchar* scanLine;
<a name="l00133"></a>00133 <span class="keywordtype">int</span> x, y;
<a name="l00134"></a>00134 <span class="keywordflow">for</span>( y=0; y<editedImage->height(); y++)
<a name="l00135"></a>00135 {
<a name="l00136"></a>00136 <span class="comment">//iterate over each selected pixel in scanline</span>
<a name="l00137"></a>00137 scanLine = editedImage->scanLine(y);
<a name="l00138"></a>00138 <span class="keywordflow">for</span>( x=0; x<editedImage->width(); x++)
<a name="l00139"></a>00139 {
<a name="l00140"></a>00140 rgb = ((QRgb*)scanLine+x);
<a name="l00141"></a>00141 grayValue = <a class="code" href="imageTools_8cpp.html#88f4928313fa9ef0e9232f3087189b65" title="find luminance of a rgb color triplet">RGBtoL</a>(rgb);
<a name="l00142"></a>00142 grayVals[(int)grayValue]++;
<a name="l00143"></a>00143 } <span class="comment">//for x</span>
<a name="l00144"></a>00144 } <span class="comment">//for y</span>
<a name="l00145"></a>00145
<a name="l00146"></a>00146 <span class="comment">//find 1% and 99% precenticles</span>
<a name="l00147"></a>00147 <span class="comment">//we'll stretch these values so we avoid outliers from affecting the stretch</span>
<a name="l00148"></a>00148 <span class="keywordtype">int</span> sum=0;
<a name="l00149"></a>00149 <span class="keywordtype">double</span> indexLow, indexHigh;
<a name="l00150"></a>00150 indexLow = -1.0; indexHigh = -1.0;
<a name="l00151"></a>00151 <span class="keywordflow">for</span>(i=0; i<256; i++)
<a name="l00152"></a>00152 {
<a name="l00153"></a>00153 sum+=grayVals[i];
<a name="l00154"></a>00154
<a name="l00155"></a>00155 <span class="comment">//if 1% not found yet and criteria met set index</span>
<a name="l00156"></a>00156 <span class="keywordflow">if</span>(indexLow < 0 &&
<a name="l00157"></a>00157 sum >= 0.01*numPixels)
<a name="l00158"></a>00158 {
<a name="l00159"></a>00159 indexLow = ((double)i)/255.0;
<a name="l00160"></a>00160 }
<a name="l00161"></a>00161
<a name="l00162"></a>00162 <span class="comment">//if 99% not found yet and criteria met set index</span>
<a name="l00163"></a>00163 <span class="keywordflow">if</span>(indexHigh < 0 &&
<a name="l00164"></a>00164 sum >= 0.99*numPixels)
<a name="l00165"></a>00165 {
<a name="l00166"></a>00166 indexHigh = ((double)i)/255.0;
<a name="l00167"></a>00167 }
<a name="l00168"></a>00168 }
<a name="l00169"></a>00169
<a name="l00170"></a>00170 <span class="comment">//only apply scaling if indexHigh > indexLow</span>
<a name="l00171"></a>00171 <span class="keywordflow">if</span>(indexHigh > indexLow)
<a name="l00172"></a>00172 {
<a name="l00173"></a>00173 <span class="comment">//run through all image pixels a second time, this time scaling coordinates as necessary</span>
<a name="l00174"></a>00174 <span class="keywordflow">for</span>( y=0; y<editedImage->height(); y++)
<a name="l00175"></a>00175 {
<a name="l00176"></a>00176 <span class="comment">//iterate over each selected pixel in scanline</span>
<a name="l00177"></a>00177 scanLine = editedImage->scanLine(y);
<a name="l00178"></a>00178 <span class="keywordflow">for</span>( x=0; x<editedImage->width(); x++)
<a name="l00179"></a>00179 {
<a name="l00180"></a>00180 <span class="comment">//get color coordinates and convert to 0-1 scale</span>
<a name="l00181"></a>00181 rgb = ((QRgb*)scanLine+x);
<a name="l00182"></a>00182 <span class="keywordtype">double</span> r = ((double)qRed(*rgb) )/255.0;
<a name="l00183"></a>00183 <span class="keywordtype">double</span> g = ((double)qGreen(*rgb) )/255.0;
<a name="l00184"></a>00184 <span class="keywordtype">double</span> <a class="code" href="jpegInternal_8h.html#f320905358fa78701e4cc60b6135601f">b</a> = ((double)qBlue(*rgb) )/255.0;
<a name="l00185"></a>00185
<a name="l00186"></a>00186 <span class="comment">//convert to hsv</span>
<a name="l00187"></a>00187 <span class="keywordtype">double</span> h,s,v;
<a name="l00188"></a>00188 <a class="code" href="imageTools_8cpp.html#7769c25727d6caedf20321d238b3828d" title="Convert a RGB color triplet to HSV.">RGBtoHSV</a>(r,g,b,&h,&s,&v);
<a name="l00189"></a>00189
<a name="l00190"></a>00190 <span class="comment">//scale and clamp v</span>
<a name="l00191"></a>00191 v = (v-indexLow)/(indexHigh-indexLow);
<a name="l00192"></a>00192
<a name="l00193"></a>00193 <span class="comment">//convert adjusted color back to rgb colorspace and clamp</span>
<a name="l00194"></a>00194 <a class="code" href="imageTools_8cpp.html#a4ea508b635b1a7648bb5834132d4681" title="Convert a HSV color triplet to RGB.">HSVtoRGB</a>( &r,&g,&b, h,s,v);
<a name="l00195"></a>00195 <span class="keywordtype">int</span> rp = (int) QMIN( QMAX((r*255), 0), 255 );
<a name="l00196"></a>00196 <span class="keywordtype">int</span> gp = (int) QMIN( QMAX((g*255), 0), 255 );
<a name="l00197"></a>00197 <span class="keywordtype">int</span> bp = (int) QMIN( QMAX((b*255), 0), 255 );
<a name="l00198"></a>00198
<a name="l00199"></a>00199 <span class="comment">//set adjusted color value</span>
<a name="l00200"></a>00200 *rgb = qRgb(rp,gp,bp);
<a name="l00201"></a>00201
<a name="l00202"></a>00202 <span class="comment">//update status bar if significant progress has been made since last update</span>
<a name="l00203"></a>00203 <span class="keywordflow">if</span>(status)
<a name="l00204"></a>00204 {
<a name="l00205"></a>00205 newProgress++;
<a name="l00206"></a>00206 <span class="keywordflow">if</span>(newProgress >= updateIncrement)
<a name="l00207"></a>00207 {
<a name="l00208"></a>00208 newProgress = 0;
<a name="l00209"></a>00209 status-><a class="code" href="classStatusWidget.html#de18735223ae40506c32c96b9c9c5476" title="Updates the progress bar by one step.">incrementProgress</a>();
<a name="l00210"></a>00210 qApp->processEvents();
<a name="l00211"></a>00211 }
<a name="l00212"></a>00212 }
<a name="l00213"></a>00213
<a name="l00214"></a>00214 } <span class="comment">//for x</span>
<a name="l00215"></a>00215 } <span class="comment">//for y</span>
<a name="l00216"></a>00216 } <span class="comment">//if scaling should be preforemd</span>
<a name="l00217"></a>00217
<a name="l00218"></a>00218 <span class="comment">//remove status bar</span>
<a name="l00219"></a>00219 <span class="keywordflow">if</span>(status)
<a name="l00220"></a>00220 {
<a name="l00221"></a>00221 status-><a class="code" href="classStatusWidget.html#02084869ff1c15dab4bc922a49b31808" title="Update message.">setStatus</a>( <span class="stringliteral">""</span> );
<a name="l00222"></a>00222 qApp->processEvents();
<a name="l00223"></a>00223 }
<a name="l00224"></a>00224 }
<a name="l00225"></a>00225 <span class="comment">//==============================================</span>
</pre></div></div>
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