gecko/gfx/thebes/gfxAlphaRecovery.cpp

/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Thebes gfx.
 *
 * The Initial Developer of the Original Code is Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2007
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Vladimir Vukicevic <vladimir@pobox.com>
 *   Bas Schouten <bschouten@mozilla.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#include "gfxAlphaRecovery.h"

#include "gfxImageSurface.h"

#define MOZILLA_SSE_INCLUDE_HEADER_FOR_SSE2
#include "mozilla/SSE.h"

/* static */ PRBool
gfxAlphaRecovery::RecoverAlpha(gfxImageSurface* blackSurf,
                               const gfxImageSurface* whiteSurf,
                               Analysis* analysis)
{
    gfxIntSize size = blackSurf->GetSize();

    if (size != whiteSurf->GetSize() ||
        (blackSurf->Format() != gfxASurface::ImageFormatARGB32 &&
         blackSurf->Format() != gfxASurface::ImageFormatRGB24) ||
        (whiteSurf->Format() != gfxASurface::ImageFormatARGB32 &&
         whiteSurf->Format() != gfxASurface::ImageFormatRGB24))
        return PR_FALSE;

#ifdef MOZILLA_MAY_SUPPORT_SSE2
    if (!analysis && mozilla::supports_sse2() &&
        RecoverAlphaSSE2(blackSurf, whiteSurf)) {
        return PR_TRUE;
    }
#endif

    blackSurf->Flush();
    whiteSurf->Flush();

    unsigned char* blackData = blackSurf->Data();
    unsigned char* whiteData = whiteSurf->Data();

    /* Get the alpha value of 'first' */
    PRUint32 first;
    if (size.width == 0 || size.height == 0) {
        first = 0;
    } else {
        if (!blackData || !whiteData)
            return PR_FALSE;

        first = RecoverPixel(*reinterpret_cast<PRUint32*>(blackData),
                             *reinterpret_cast<PRUint32*>(whiteData));
    }

    PRUint32 deltas = 0;
    for (PRInt32 i = 0; i < size.height; ++i) {
        PRUint32* blackPixel = reinterpret_cast<PRUint32*>(blackData);
        const PRUint32* whitePixel = reinterpret_cast<PRUint32*>(whiteData);
        for (PRInt32 j = 0; j < size.width; ++j) {
            PRUint32 recovered = RecoverPixel(blackPixel[j], whitePixel[j]);
            blackPixel[j] = recovered;
            deltas |= (first ^ recovered);
        }
        blackData += blackSurf->Stride();
        whiteData += whiteSurf->Stride();
    }

    blackSurf->MarkDirty();
    
    if (analysis) {
        analysis->uniformAlpha = (deltas >> 24) == 0;
        analysis->uniformColor = PR_FALSE;
        if (analysis->uniformAlpha) {
            double d_first_alpha = first >> 24;
            analysis->alpha = d_first_alpha/255.0;
            /* we only set uniformColor when the alpha is already uniform.
               it's only useful in that case ... and if the alpha was nonuniform
               then computing whether the color is uniform would require unpremultiplying
               every pixel */
            analysis->uniformColor = deltas == 0;
            if (analysis->uniformColor) {
                if (d_first_alpha == 0.0) {
                    /* can't unpremultiply, this is OK */
                    analysis->r = analysis->g = analysis->b = 0.0;
                } else {
                    analysis->r = (first & 0xFF)/d_first_alpha;
                    analysis->g = ((first >> 8) & 0xFF)/d_first_alpha;
                    analysis->b = ((first >> 16) & 0xFF)/d_first_alpha;
                }
            }
        }
    }

    return PR_TRUE;
}