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|
/*
/--------------------------------------------------------------------
|
| $Id: plfiltercontrast.cpp,v 1.11 2004/09/11 12:41:36 uzadow Exp $
|
| Copyright (c) 1996-2002 Ulrich von Zadow
|
\--------------------------------------------------------------------
*/
#include "plfiltercontrast.h"
#include "plbitmap.h"
#include "plpaintlibdefs.h"
PLFilterContrast::PLFilterContrast(double contrast, PLBYTE offset)
: PLFilter(),
m_contrast(contrast),
m_offset((double) offset-128.0)
{
}
PLFilterContrast::~PLFilterContrast()
{
}
void PLFilterContrast::Apply(PLBmpBase * pBmpSource, PLBmp * pBmpDest) const
{
// Consider a coordinate system with two axes: The x axis represents
// an input RGB component or intensity, the y axis an output RGB
// component or intensity. The ranges of input and output values go
// from 0 - 255.
// If I take a straight line that intersects (0,0) through (255,255),
// I have defined a Null filter that leaves the image unchanged.
// Next step: Let's rotate this straight line around the point (128,128).
// If I increase the slope, output values above (128,128) are increased
// by the slope factor, output values below (128, 128) are decreased
// likewise. This is how I create the contrast enhancement effect.
// Now we are having a problem: Increasing the slope means that our
// straight line intersects the line (x, 255), creating output values
// above 255 which are not defined in our RGB model. Since in the RGB world
// there is nothing whiter than white, I'll set all these values to 255. A
// similar thing happens on the lower left of our imaginary diagram: All
// values smaller than 0 have to be set 0 - according to the fact that
// there is nothing darker than absolute darkness...
// Ok, now what is that offset value good for? Remember the point
// (128,128). At this position, input and output values of our filter
// remain unchanged, independent of the slope of our straight line. Now
// imagine we are shifting our line parallel to the x axis. Our filter
// works quite differently now: We create a cut-off for the higher output
// value range (shift right), or the lower ones (shift left).
int total = 0;
register int inc;
double contrast = m_contrast;
PLASSERT (pBmpSource->GetBitsPerPixel() >= 24);
pBmpDest->Create (pBmpSource->GetWidth(),
pBmpSource->GetHeight(),
pBmpSource->GetPixelFormat(),
NULL, 0,
pBmpSource->GetResolution());
PLBYTE ** pSrcLines = pBmpSource->GetLineArray();
PLBYTE ** pDstLines = pBmpDest->GetLineArray();
register int destWidth = pBmpDest->GetWidth();
if(pBmpSource->GetBitsPerPixel() == 24)
inc = 3;
if(pBmpSource->GetBitsPerPixel() == 32)
inc = sizeof(PLPixel32);
register double red, green, blue;
register double csupp = contrast * (m_offset - 128.0) + 128.0;
for (int y = 0; y < pBmpDest->GetHeight(); ++y)
{ // For each line
register PLBYTE * pSrcPixel = pSrcLines[y];
register PLBYTE * pDstPixel = pDstLines[y];
for (register int x = 0; x < destWidth; ++x)
{
// Formel fr Kontrastberechnung:
// v = (contrast * (v - 12580 + m_offset) + 128.0);
red = contrast * ((double) (pSrcPixel[PL_RGBA_RED])) + csupp;
green = contrast * ((double) (pSrcPixel[PL_RGBA_GREEN])) + csupp;
blue = contrast * ((double) (pSrcPixel[PL_RGBA_BLUE])) + csupp;
if(red >= 255.0)
pDstPixel[PL_RGBA_RED] = (PLBYTE) 255;
else if (red < 0.0)
pDstPixel[PL_RGBA_RED] = (PLBYTE) 0;
else
pDstPixel[PL_RGBA_RED] = (PLBYTE) red;
if(green >= 255.0)
pDstPixel[PL_RGBA_GREEN] = (PLBYTE) 255;
else if (green < 0.0)
pDstPixel[PL_RGBA_GREEN] = (PLBYTE) 0;
else
pDstPixel[PL_RGBA_GREEN] = (PLBYTE) green;
if(blue >= 255.0)
pDstPixel[PL_RGBA_BLUE] = (PLBYTE) 255;
else if (blue < 0.0)
pDstPixel[PL_RGBA_BLUE] = (PLBYTE) 0;
else
pDstPixel[PL_RGBA_BLUE] = (PLBYTE) blue;
pSrcPixel += inc;
pDstPixel += inc;
}
}
}
/*
/--------------------------------------------------------------------
|
| $Log: plfiltercontrast.cpp,v $
| Revision 1.11 2004/09/11 12:41:36 uzadow
| removed plstdpch.h
|
| Revision 1.10 2004/09/09 16:52:45 artcom
| refactored PixelFormat
|
| Revision 1.9 2004/06/15 10:26:13 uzadow
| Initial nonfunctioning version of plbmpbase.
|
| Revision 1.8 2003/11/05 15:17:26 artcom
| Added ability to specify initial data in PLBitmap::Create()
|
| Revision 1.7 2003/08/23 14:00:02 uzadow
| no message
|
| Revision 1.6 2002/08/04 20:08:01 uzadow
| Added PLBmpInfo class, ability to extract metainformation from images without loading the whole image and proper greyscale support.
|
| Revision 1.5 2002/03/31 13:36:42 uzadow
| Updated copyright.
|
| Revision 1.4 2001/10/16 17:12:26 uzadow
| Added support for resolution information (Luca Piergentili)
|
| Revision 1.3 2001/10/06 22:03:26 uzadow
| Added PL prefix to basic data types.
|
| Revision 1.2 2001/10/06 15:32:22 uzadow
| Removed types LPBYTE, DWORD, UCHAR, VOID and INT from the code.
|
| Revision 1.1 2001/09/16 19:03:23 uzadow
| Added global name prefix PL, changed most filenames.
|
| Revision 1.5 2001/02/04 14:31:52 uzadow
| Member initialization list cleanup (Erik Hoffmann).
|
| Revision 1.4 2001/01/15 15:05:31 uzadow
| Added PLBmp::ApplyFilter() and PLBmp::CreateFilteredCopy()
|
| Revision 1.3 2001/01/12 23:30:01 uzadow
| Doc update.
|
| Revision 1.2 2000/12/18 22:42:53 uzadow
| Replaced RGBAPIXEL with PLPixel32.
|
| Revision 1.1 2000/11/06 23:20:22 uzadow
| Added Contrast, Intensity and Lightness filters by
| Thomas Hirschmann
|
|
\--------------------------------------------------------------------
*/
|
