source: liacs/MIR2010/SourceCode/cximage/ximalpha.cpp@ 107

// xImalpha.cpp : Alpha channel functions
/* 07/08/2001 v1.00 - Davide Pizzolato - www.xdp.it
 * CxImage version 6.0.0 02/Feb/2008
 */

#include "ximage.h"

#if CXIMAGE_SUPPORT_ALPHA

////////////////////////////////////////////////////////////////////////////////
/**
 * \sa AlphaSetMax
 */
BYTE CxImage::AlphaGetMax() const
{
        return info.nAlphaMax;
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Sets global Alpha (opacity) value applied to the whole image,
 * valid only for painting functions.
 * \param nAlphaMax: can be from 0 to 255
 */
void CxImage::AlphaSetMax(BYTE nAlphaMax)
{
        info.nAlphaMax=nAlphaMax;
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Checks if the image has a valid alpha channel.
 */
bool CxImage::AlphaIsValid()
{
        return pAlpha!=0;
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Enables the alpha palette, so the Draw() function changes its behavior.
 */
void CxImage::AlphaPaletteEnable(bool enable)
{
        info.bAlphaPaletteEnabled=enable;
}
////////////////////////////////////////////////////////////////////////////////
/**
 * True if the alpha palette is enabled for painting.
 */
bool CxImage::AlphaPaletteIsEnabled()
{
        return info.bAlphaPaletteEnabled;
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Sets the alpha channel to full transparent. AlphaSet(0) has the same effect
 */
void CxImage::AlphaClear()
{
        if (pAlpha)     memset(pAlpha,0,head.biWidth * head.biHeight);
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Sets the alpha level for the whole image.
 * \param level : from 0 (transparent) to 255 (opaque)
 */
void CxImage::AlphaSet(BYTE level)
{
        if (pAlpha)     memset(pAlpha,level,head.biWidth * head.biHeight);
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Allocates an empty (opaque) alpha channel.
 */
bool CxImage::AlphaCreate()
{
        if (pAlpha==NULL) {
                pAlpha = (BYTE*)malloc(head.biWidth * head.biHeight);
                if (pAlpha) memset(pAlpha,255,head.biWidth * head.biHeight);
        }
        return (pAlpha!=0);
}
////////////////////////////////////////////////////////////////////////////////
void CxImage::AlphaDelete()
{
        if (pAlpha) { free(pAlpha); pAlpha=0; }
}
////////////////////////////////////////////////////////////////////////////////
void CxImage::AlphaInvert()
{
        if (pAlpha) {
                BYTE *iSrc=pAlpha;
                long n=head.biHeight*head.biWidth;
                for(long i=0; i < n; i++){
                        *iSrc=(BYTE)~(*(iSrc));
                        iSrc++;
                }
        }
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Imports an existing alpa channel from another image with the same width and height.
 */
bool CxImage::AlphaCopy(CxImage &from)
{
        if (from.pAlpha == NULL || head.biWidth != from.head.biWidth || head.biHeight != from.head.biHeight) return false;
        if (pAlpha==NULL) pAlpha = (BYTE*)malloc(head.biWidth * head.biHeight);
        if (pAlpha==NULL) return false;
        memcpy(pAlpha,from.pAlpha,head.biWidth * head.biHeight);
        info.nAlphaMax=from.info.nAlphaMax;
        return true;
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Creates the alpha channel from a gray scale image.
 */
bool CxImage::AlphaSet(CxImage &from)
{
        if (!from.IsGrayScale() || head.biWidth != from.head.biWidth || head.biHeight != from.head.biHeight) return false;
        if (pAlpha==NULL) pAlpha = (BYTE*)malloc(head.biWidth * head.biHeight);
        BYTE* src = from.info.pImage;
        BYTE* dst = pAlpha;
        if (src==NULL || dst==NULL) return false;
        for (long y=0; y<head.biHeight; y++){
                memcpy(dst,src,head.biWidth);
                dst += head.biWidth;
                src += from.info.dwEffWidth;
        }
        return true;
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Sets the alpha level for a single pixel 
 */
void CxImage::AlphaSet(const long x,const long y,const BYTE level)
{
        if (pAlpha && IsInside(x,y)) pAlpha[x+y*head.biWidth]=level;
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Gets the alpha level for a single pixel 
 */
BYTE CxImage::AlphaGet(const long x,const long y)
{
        if (pAlpha && IsInside(x,y)) return pAlpha[x+y*head.biWidth];
        return 0;
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Returns pointer to alpha data for pixel (x,y).
 *
 * \author ***bd*** 2.2004
 */
BYTE* CxImage::AlphaGetPointer(const long x,const long y)
{
        if (pAlpha && IsInside(x,y)) return pAlpha+x+y*head.biWidth;
        return 0;
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Get alpha value without boundscheck (a bit faster). Pixel must be inside the image.
 *
 * \author ***bd*** 2.2004
 */
BYTE CxImage::BlindAlphaGet(const long x,const long y)
{
#ifdef _DEBUG
        if (!IsInside(x,y) || (pAlpha==0))
  #if CXIMAGE_SUPPORT_EXCEPTION_HANDLING
                throw 0;
  #else
                return 0;
  #endif
#endif
        return pAlpha[x+y*head.biWidth];
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Resets the alpha palette 
 */
void CxImage::AlphaPaletteClear()
{
        RGBQUAD c;
        for(WORD ip=0; ip<head.biClrUsed;ip++){
                c=GetPaletteColor((BYTE)ip);
                c.rgbReserved=0;
                SetPaletteColor((BYTE)ip,c);
        }
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Checks if the image has a valid alpha palette. 
 */
bool CxImage::AlphaPaletteIsValid()
{
        RGBQUAD c;
        for(WORD ip=0; ip<head.biClrUsed;ip++){
                c=GetPaletteColor((BYTE)ip);
                if (c.rgbReserved != 0) return true;
        }
        return false;
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Blends the alpha channel and the alpha palette with the pixels. The result is a 24 bit image.
 * The background color can be selected using SetTransColor().
 */
void CxImage::AlphaStrip()
{
        bool bAlphaPaletteIsValid = AlphaPaletteIsValid();
        bool bAlphaIsValid = AlphaIsValid();
        if (!(bAlphaIsValid || bAlphaPaletteIsValid)) return;
        RGBQUAD c;
        long a, a1;
        if (head.biBitCount==24){
                for(long y=0; y<head.biHeight; y++){
                        for(long x=0; x<head.biWidth; x++){
                                c = BlindGetPixelColor(x,y);
                                if (bAlphaIsValid) a=(BlindAlphaGet(x,y)*info.nAlphaMax)/255; else a=info.nAlphaMax;
                                a1 = 256-a;
                                c.rgbBlue = (BYTE)((c.rgbBlue * a + a1 * info.nBkgndColor.rgbBlue)>>8);
                                c.rgbGreen = (BYTE)((c.rgbGreen * a + a1 * info.nBkgndColor.rgbGreen)>>8);
                                c.rgbRed = (BYTE)((c.rgbRed * a + a1 * info.nBkgndColor.rgbRed)>>8);
                                BlindSetPixelColor(x,y,c);
                        }
                }
                AlphaDelete();
        } else {
                CxImage tmp(head.biWidth,head.biHeight,24);
                if (!tmp.IsValid()){
                        strcpy(info.szLastError,tmp.GetLastError());
                        return;
                }

                for(long y=0; y<head.biHeight; y++){
                        for(long x=0; x<head.biWidth; x++){
                                c = BlindGetPixelColor(x,y);
                                if (bAlphaIsValid) a=(BlindAlphaGet(x,y)*info.nAlphaMax)/255; else a=info.nAlphaMax;
                                if (bAlphaPaletteIsValid) a=(c.rgbReserved*a)/255;
                                a1 = 256-a;
                                c.rgbBlue = (BYTE)((c.rgbBlue * a + a1 * info.nBkgndColor.rgbBlue)>>8);
                                c.rgbGreen = (BYTE)((c.rgbGreen * a + a1 * info.nBkgndColor.rgbGreen)>>8);
                                c.rgbRed = (BYTE)((c.rgbRed * a + a1 * info.nBkgndColor.rgbRed)>>8);
                                tmp.BlindSetPixelColor(x,y,c);
                        }
                }
                Transfer(tmp);
        }
        return;
}
////////////////////////////////////////////////////////////////////////////////
bool CxImage::AlphaFlip()
{
        if (!pAlpha) return false;

        BYTE *buff = (BYTE*)malloc(head.biWidth);
        if (!buff) return false;

        BYTE *iSrc,*iDst;
        iSrc = pAlpha + (head.biHeight-1)*head.biWidth;
        iDst = pAlpha;
        for (long i=0; i<(head.biHeight/2); ++i)
        {
                memcpy(buff, iSrc, head.biWidth);
                memcpy(iSrc, iDst, head.biWidth);
                memcpy(iDst, buff, head.biWidth);
                iSrc-=head.biWidth;
                iDst+=head.biWidth;
        }

        free(buff);

        return true;
}
////////////////////////////////////////////////////////////////////////////////
bool CxImage::AlphaMirror()
{
        if (!pAlpha) return false;
        BYTE* pAlpha2 = (BYTE*)malloc(head.biWidth * head.biHeight);
        if (!pAlpha2) return false;
        BYTE *iSrc,*iDst;
        long wdt=head.biWidth-1;
        iSrc=pAlpha + wdt;
        iDst=pAlpha2;
        for(long y=0; y < head.biHeight; y++){
                for(long x=0; x <= wdt; x++)
                        *(iDst+x)=*(iSrc-x);
                iSrc+=head.biWidth;
                iDst+=head.biWidth;
        }
        free(pAlpha);
        pAlpha=pAlpha2;
        return true;
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Exports the alpha channel in a 8bpp grayscale image. 
 */
bool CxImage::AlphaSplit(CxImage *dest)
{
        if (!pAlpha || !dest) return false;

        CxImage tmp(head.biWidth,head.biHeight,8);
        if (!tmp.IsValid()){
                strcpy(info.szLastError,tmp.GetLastError());
                return false;
        }

        for(long y=0; y<head.biHeight; y++){
                for(long x=0; x<head.biWidth; x++){
                        tmp.BlindSetPixelIndex(x,y,pAlpha[x+y*head.biWidth]);
                }
        }

        tmp.SetGrayPalette();
        dest->Transfer(tmp);

        return true;
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Exports the alpha palette channel in a 8bpp grayscale image. 
 */
bool CxImage::AlphaPaletteSplit(CxImage *dest)
{
        if (!AlphaPaletteIsValid() || !dest) return false;

        CxImage tmp(head.biWidth,head.biHeight,8);
        if (!tmp.IsValid()){
                strcpy(info.szLastError,tmp.GetLastError());
                return false;
        }

        for(long y=0; y<head.biHeight; y++){
                for(long x=0; x<head.biWidth; x++){
                        tmp.BlindSetPixelIndex(x,y,BlindGetPixelColor(x,y).rgbReserved);
                }
        }

        tmp.SetGrayPalette();
        dest->Transfer(tmp);

        return true;
}
////////////////////////////////////////////////////////////////////////////////
/**
 * Merge in the alpha layer the transparent color mask
 * (previously set with SetTransColor or SetTransIndex) 
 */
bool CxImage::AlphaFromTransparency()
{
        if (!IsValid() || !IsTransparent())
                return false;

        AlphaCreate();

        for(long y=0; y<head.biHeight; y++){
                for(long x=0; x<head.biWidth; x++){
                        if (IsTransparent(x,y)){
                                AlphaSet(x,y,0);
                        }
                }
        }
        return true;
}
////////////////////////////////////////////////////////////////////////////////
#endif //CXIMAGE_SUPPORT_ALPHA