tilt_internal.h File Reference

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Classes

class  DPoint

Functions

QRgb interpolatedPixelValue (double xp, double yp, QImage *image)
QRgb blendColors (QRgb color1, QRgb color2, double alpha)
DPoint findTwoLineIntersection (DPoint p1, DPoint p2, DPoint p3, DPoint p4)


Function Documentation

QRgb blendColors ( QRgb  color1,
QRgb  color2,
double  alpha 
)

Definition at line 359 of file tilt.cpp.

Referenced by interpolatedPixelValue().

00360 {
00361   double alpha2 = 1.0-alpha;
00362   return qRgb( (int) QMAX( QMIN( 255, alpha2*qRed  (color1) + alpha*qRed(color2)   ), 0 ),
00363                (int) QMAX( QMIN( 255, alpha2*qGreen(color1) + alpha*qGreen(color2) ), 0 ),
00364                (int) QMAX( QMIN( 255, alpha2*qBlue (color1) + alpha*qBlue(color2)  ), 0 ) );
00365 }

DPoint findTwoLineIntersection ( DPoint  p1,
DPoint  p2,
DPoint  p3,
DPoint  p4 
)

Definition at line 367 of file tilt.cpp.

References DPoint::x(), and DPoint::y().

Referenced by correctImageTilt().

00369 {
00370   //----------------------------------------------
00371   //=== Case 1: neither line has a change in X ===
00372   //----------------------------------------------
00373   //If there is no change in x for both lines, 
00374   //either lines will NEVER or ALWAYS intersect.
00375   if(p1.x() == p2.x() &&
00376      p4.x() == p3.x())
00377   {
00378     //Ok, if their x values are equal, return 
00379     //intersection point as line A's point A.
00380     //Yes, this is a little arbitratry. But 
00381     //theoreticaly this section of code will almost
00382     //never be executed.
00383     if( p1.x() == p3.x() )
00384     { return DPoint( p1.x(), p1.y() ); }
00385     //Else lines will never intersect,
00386     //return pair (-32000,-32000)
00387     else
00388     { return DPoint( -32000, -32000 ); }
00389   } 
00390   //----------------------------------------------
00391   //Else, we know at least one of the lines 
00392   //does NOT have a slope of infinity!!!
00393   //----------------------------------------------
00394   
00395   //----------------------------------------------
00396   //=== Case 2: line A has no change in X      ===
00397   //----------------------------------------------
00398   //If line A has an infinite slope (no change in x)
00399   //we know line B does not have an infinite slope...
00400   else if( p1.x() == p2.x() )
00401   {
00402     double slopeB = ((double) (p4.y() - p3.y()) ) / (p4.x() - p3.x());
00403     
00404     double yInterceptB = p3.y() - slopeB*p3.x();
00405     
00406     //y = mx+b
00407     return DPoint( p2.x(), slopeB*p2.x() + yInterceptB );
00408   }
00409   //----------------------------------------------
00410   //=== Case 3: line B has no change in X      ===
00411   //----------------------------------------------
00412   //If line B has an infinite slope (no change in x)
00413   //we know line A does not have an infinite slope...
00414   else if( p4.x() == p3.x() )
00415   {
00416     double slopeA = ((double) (p2.y() - p1.y()) ) / (p2.x() - p1.x());
00417     
00418     double yInterceptA = p1.y() - slopeA*p1.x();
00419     
00420     //y = mx+b
00421     return DPoint( p4.x(), slopeA*p4.x() + yInterceptA );
00422   }
00423   //----------------------------------------------
00424   //=== Case 4: both lines have non infinite slopes ===
00425   //----------------------------------------------
00426   else
00427   {
00428     double slopeA = ((double) (p2.y() - p1.y()) ) / (p2.x() - p1.x());
00429     double slopeB = ((double) (p4.y() - p3.y()) ) / (p4.x() - p3.x());
00430     double yInterceptA = p1.y() - slopeA*p1.x();
00431     double yInterceptB = p3.y() - slopeB*p3.x();
00432     
00433     //y1 = mx1+b
00434     //y2 = nx2+c
00435     //at intersection y1=y2 and x1 = x2 so...
00436     //mx +b = nx + c
00437     //x(m-n) = c-b
00438     //x = (c-b)/(m-n)
00439     //where m and n are slope and
00440     //b and c are y-intercepts.
00441     //x = (c-b)/(m-n)
00442     double x = (yInterceptB - yInterceptA) / (slopeA - slopeB);
00443     return DPoint( x, (slopeA * x) + yInterceptA );
00444   }
00445 }

QRgb interpolatedPixelValue ( double  xp,
double  yp,
QImage *  image 
)

Definition at line 312 of file tilt.cpp.

References blendColors(), height, and width.

Referenced by correctImageTilt().

00314 {
00315   //do boundary checking to 
00316   //ensure we don't read beyond image boundaries
00317   if(xp < 0 || xp >= image->width() ||
00318      yp < 0 || yp >= image->height() )
00319     return qRgb( 0, 0, 0 );
00320 
00321   //get four pixel colors, 
00322   int x = (int)xp;
00323   int y = (int)yp;
00324   
00325   uchar* scanLine1 = image->scanLine( y );
00326 
00327   uchar* scanLine2;
00328   if( y < image->height() - 1 )
00329     scanLine2 = image->scanLine( y+1 );
00330   else
00331     scanLine2 = scanLine1;
00332   
00333   QRgb p1,p2,p3,p4;
00334   
00335   p1 = *((QRgb*)scanLine1+x);
00336   p3 = *((QRgb*)scanLine2+x);
00337         
00338   if( x < image->width() - 1)
00339   {
00340     p2 = *((QRgb*)scanLine1+x+1);
00341     p4 = *((QRgb*)scanLine2+x+1);     
00342   }
00343   else
00344   {
00345     p2 = p1;
00346     p4 = p3;
00347   }
00348   
00349   //blend four colors
00350   double alphaY = yp - y;
00351   double alphaX = xp - x;
00352   
00353   p1 = blendColors( p1, p2, alphaX );
00354   p3 = blendColors( p3, p4, alphaX );
00355   p1 = blendColors( p1, p3, alphaY );
00356   return p1;
00357 }


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