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emboss.cpp

//==============================================
//  copyright            : (C) 2003-2005 by Will Stokes
//==============================================
//  This program is free software; you can redistribute it
//  and/or modify it under the terms of the GNU General
//  Public License as published by the Free Software
//  Foundation; either version 2 of the License, or
//  (at your option) any later version.
//==============================================

//Systemwide includes
#include <qimage.h>
#include <qstring.h>
#include <qapplication.h>
#include <math.h>

//Projectwide includes
#include "emboss.h"
#include "manipulationOptions.h"
#include "../tools/imageTools.h"
#include "../../gui/statusWidget.h"

//----------------------------------------------
// Inputs:
// -------
// QString filename - location of original image on disk
// StatusWidget* status - widget for making progress visible to user
//
// Outputs:
// --------
// QImage* returned - constructed image
//
// Description:
// ------------
// This method constructs an embossed version of
// the image by modifying the luminance of each pixel
// by taking a weighted average of pixel luminance within
// a local neighborhood. Most embossing algorithms convert an 
// image to grayscale and then combine a pixel's gray value with
// its neighbors using the following convolution matrix:
//
// [ -1  -1   0
//   -1   1   1
//    0   1   1 ]
//
// This apporach has two problems. First, all color information
// is lost. Second, the convolution filter is not a function of image
// size, and as a result embossing results on high resolution images are
// barely when viewed on a high resolution screen or printed at high DPI. 
// 
// My solution to this problem is to:
//
// 1.) Apply the emboss effect on pixel luminance and leave pixel
// color untouched. The varying lightness that results produces
// the same effect, and if a grayscale image is really desired the
// image can be converted to grayscale either before or after the 
// emboss effect takes place.
// 
// 2.) using neighboring pixels that are a distance D from the 
// pixel being modified in the X or Y dimensions. This simply 
// modification allows the embossing procedure to run at the 
// same speed (larger convolution matrices would slow the algorithm 
// to at best O(N^2 * M^2) where there are N^2 pixels in the image 
// and the convolution matrix is M^2 in size) while providing the 
// same effective emboss effect at any image resolution. This is 
// done by computing distance D using the minimum image dimension:
//
// D = MIN( width, height )
//
// At each pixel, we compute an average luminance of the 6 
// neighbors and combine these values with a 50% luminance value for 
// the pixel in question. This luminance value is used to replace 
// the current pixel luminance before converting it back to RGB 
// space and storing in the edited image object.
//
// Neighbor pixels that are clamped to be on the image plane to 
// prevent lookups of neighbor pixels with negative coordinates or
// coordinates beyond the width/height of the image in question.
//----------------------------------------------

//==============================================
QImage* embossEffect( QString filename, ManipulationOptions* options )
{
  //load original image  
  QImage originalImage( filename );

  //convert to 32-bit depth if necessary
  if( originalImage.depth() < 32 ) { originalImage = originalImage.convertDepth( 32, Qt::AutoColor ); }
  
  //create edited image
  QImage* editedImage = new QImage( filename );

  //convert to 32-bit depth if necessary
  if( editedImage->depth() < 32 )
  {
    QImage* tmp = editedImage;
    editedImage = new QImage( tmp->convertDepth( 32, Qt::AutoColor ) );
    delete tmp; tmp=NULL;
  }
  
  //determine if busy indicators will be used
  bool useBusyIndicators = false;
  StatusWidget* status = NULL;
  if( options != NULL && options->getStatus() != NULL )
  {
    useBusyIndicators = true;
    status = options->getStatus(); 
  }
  
  //setup progress bar
  if(useBusyIndicators)
  {
    QString statusMessage = qApp->translate( "embossEffect", "Applying Emboss Effect:" );
    status->showProgressBar( statusMessage, 100 );
    qApp->processEvents();  
  }
  
  //update progress bar for every 1% of completion
  const int updateIncrement = (int) ( 0.01 * originalImage.width() * originalImage.height() );
  int newProgress = 0; 

  //iterate over each selected scanline 
  int x, y;
  QRgb* rgb;
  uchar* scanLine;

  int yPrev, yNext, xPrev, xNext;
  
  //compute the radius using image resolution
  double minDimen = (double) QMIN( editedImage->width(), editedImage->height() );  
  const int embossRadius = (int) QMAX( 1, (sqrt(minDimen)/8) );
  
  for( y=0; y<editedImage->height(); y++)
  {   
    scanLine = originalImage.scanLine(y);

    //compute previous and next y pixel coordinates
    yPrev = QMAX( y-embossRadius, 0 );
    yNext = QMIN( y+embossRadius, editedImage->height() - 1 );
    
    //iterate over each selected pixel in scanline
    for( x=0; x<editedImage->width(); x++)
    {
      //compute previous and next x  pixel coordinates
      xPrev = QMAX( x-embossRadius, 0 );
      xNext = QMIN( x+embossRadius, editedImage->width() - 1 );

      //start with a default luminance of 128 (50% luminance)
      int sum = 128;
      
      //sum weighted gray values of neighbors
      scanLine = originalImage.scanLine( yPrev );
      sum-= qGray( *((QRgb*)scanLine + xPrev ) );
      sum-= qGray( *((QRgb*)scanLine + x ) );

      scanLine = originalImage.scanLine( y );
      sum-= qGray( *((QRgb*)scanLine + xPrev ) );
      sum+= qGray( *((QRgb*)scanLine + xNext ) );

      scanLine = originalImage.scanLine( yNext );
      sum+= qGray( *((QRgb*)scanLine + x ) );
      sum+= qGray( *((QRgb*)scanLine + xNext ) );
      
      //clamp sum to within 0-255 range
      sum = QMAX( QMIN( sum, 255), 0 );

      //get original pixel color in HSV space
      scanLine = editedImage->scanLine(y);            
      rgb = ((QRgb*)scanLine+x);
      double r = ((double)qRed(*rgb)   )/255.0;
      double g = ((double)qGreen(*rgb) )/255.0;
      double b = ((double)qBlue(*rgb)  )/255.0;
      
      //convert to hsv
      double h,s,v;
      RGBtoHSV(r,g,b,&h,&s,&v);
      
      //reset v
      v = ((double)sum)/255;
      
      //convert adjusted color back to rgb colorspace and clamp
      HSVtoRGB( &r,&g,&b, h,s,v);         
      int rp = (int) QMIN( QMAX((r*255), 0), 255 );
      int gp = (int) QMIN( QMAX((g*255), 0), 255 );
      int bp = (int) QMIN( QMAX((b*255), 0), 255 );
      
      //set adjusted color value
      *rgb = qRgb(rp,gp,bp);
      
      //update status bar if significant progress has been made since last update
      if(useBusyIndicators)
      {
        newProgress++;
        if(newProgress >= updateIncrement)
        {
          newProgress = 0;
          status->incrementProgress();
          qApp->processEvents();  
        }
      }
      
    }
  }
  
  //return pointer to edited image
  return editedImage;  
}
//==============================================

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