root/Source/platform/graphics/filters/FEComponentTransfer.cpp

DEFINITIONS

1. m_alphaFunc
2. create
3. redFunction
4. setRedFunction
5. greenFunction
6. setGreenFunction
7. blueFunction
8. setBlueFunction
9. alphaFunction
10. setAlphaFunction
11. identity
12. table
13. discrete
14. linear
15. gamma
16. applySoftware
17. affectsTransparentPixels
18. createImageFilter
19. getValues
20. externalRepresentation

/*
 * Copyright (C) 2004, 2005, 2006, 2007 Nikolas Zimmermann <zimmermann@kde.org>
 * Copyright (C) 2004, 2005 Rob Buis <buis@kde.org>
 * Copyright (C) 2005 Eric Seidel <eric@webkit.org>
 * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
 * Copyright (C) Research In Motion Limited 2010. All rights reserved.
 * Copyright (C) 2013 Google Inc. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

#include "config.h"
#include "platform/graphics/filters/FEComponentTransfer.h"

#include "SkColorFilterImageFilter.h"
#include "SkTableColorFilter.h"
#include "platform/graphics/GraphicsContext.h"
#include "platform/graphics/filters/SkiaImageFilterBuilder.h"
#include "platform/graphics/skia/NativeImageSkia.h"
#include "platform/text/TextStream.h"
#include "wtf/MathExtras.h"
#include "wtf/StdLibExtras.h"
#include "wtf/Uint8ClampedArray.h"

namespace WebCore {

typedef void (*TransferType)(unsigned char*, const ComponentTransferFunction&);

FEComponentTransfer::FEComponentTransfer(Filter* filter, const ComponentTransferFunction& redFunc, const ComponentTransferFunction& greenFunc,
    const ComponentTransferFunction& blueFunc, const ComponentTransferFunction& alphaFunc)
    : FilterEffect(filter)
    , m_redFunc(redFunc)
    , m_greenFunc(greenFunc)
    , m_blueFunc(blueFunc)
    , m_alphaFunc(alphaFunc)
{
}

PassRefPtr<FEComponentTransfer> FEComponentTransfer::create(Filter* filter, const ComponentTransferFunction& redFunc,
    const ComponentTransferFunction& greenFunc, const ComponentTransferFunction& blueFunc, const ComponentTransferFunction& alphaFunc)
{
    return adoptRef(new FEComponentTransfer(filter, redFunc, greenFunc, blueFunc, alphaFunc));
}

ComponentTransferFunction FEComponentTransfer::redFunction() const
{
    return m_redFunc;
}

void FEComponentTransfer::setRedFunction(const ComponentTransferFunction& func)
{
    m_redFunc = func;
}

ComponentTransferFunction FEComponentTransfer::greenFunction() const
{
    return m_greenFunc;
}

void FEComponentTransfer::setGreenFunction(const ComponentTransferFunction& func)
{
    m_greenFunc = func;
}

ComponentTransferFunction FEComponentTransfer::blueFunction() const
{
    return m_blueFunc;
}

void FEComponentTransfer::setBlueFunction(const ComponentTransferFunction& func)
{
    m_blueFunc = func;
}

ComponentTransferFunction FEComponentTransfer::alphaFunction() const
{
    return m_alphaFunc;
}

void FEComponentTransfer::setAlphaFunction(const ComponentTransferFunction& func)
{
    m_alphaFunc = func;
}

static void identity(unsigned char*, const ComponentTransferFunction&)
{
}

static void table(unsigned char* values, const ComponentTransferFunction& transferFunction)
{
    const Vector<float>& tableValues = transferFunction.tableValues;
    unsigned n = tableValues.size();
    if (n < 1)
        return;
    for (unsigned i = 0; i < 256; ++i) {
        double c = i / 255.0;
        unsigned k = static_cast<unsigned>(c * (n - 1));
        double v1 = tableValues[k];
        double v2 = tableValues[std::min((k + 1), (n - 1))];
        double val = 255.0 * (v1 + (c * (n - 1) - k) * (v2 - v1));
        val = std::max(0.0, std::min(255.0, val));
        values[i] = static_cast<unsigned char>(val);
    }
}

static void discrete(unsigned char* values, const ComponentTransferFunction& transferFunction)
{
    const Vector<float>& tableValues = transferFunction.tableValues;
    unsigned n = tableValues.size();
    if (n < 1)
        return;
    for (unsigned i = 0; i < 256; ++i) {
        unsigned k = static_cast<unsigned>((i * n) / 255.0);
        k = std::min(k, n - 1);
        double val = 255 * tableValues[k];
        val = std::max(0.0, std::min(255.0, val));
        values[i] = static_cast<unsigned char>(val);
    }
}

static void linear(unsigned char* values, const ComponentTransferFunction& transferFunction)
{
    for (unsigned i = 0; i < 256; ++i) {
        double val = transferFunction.slope * i + 255 * transferFunction.intercept;
        val = std::max(0.0, std::min(255.0, val));
        values[i] = static_cast<unsigned char>(val);
    }
}

static void gamma(unsigned char* values, const ComponentTransferFunction& transferFunction)
{
    for (unsigned i = 0; i < 256; ++i) {
        double exponent = transferFunction.exponent; // RCVT doesn't like passing a double and a float to pow, so promote this to double
        double val = 255.0 * (transferFunction.amplitude * pow((i / 255.0), exponent) + transferFunction.offset);
        val = std::max(0.0, std::min(255.0, val));
        values[i] = static_cast<unsigned char>(val);
    }
}

void FEComponentTransfer::applySoftware()
{
    FilterEffect* in = inputEffect(0);
    ImageBuffer* resultImage = createImageBufferResult();
    if (!resultImage)
        return;

    RefPtr<Image> image = in->asImageBuffer()->copyImage(DontCopyBackingStore);
    RefPtr<NativeImageSkia> nativeImage = image->nativeImageForCurrentFrame();
    if (!nativeImage)
        return;

    unsigned char rValues[256], gValues[256], bValues[256], aValues[256];
    getValues(rValues, gValues, bValues, aValues);

    IntRect destRect = drawingRegionOfInputImage(in->absolutePaintRect());
    SkPaint paint;
    paint.setColorFilter(SkTableColorFilter::CreateARGB(aValues, rValues, gValues, bValues))->unref();
    paint.setXfermodeMode(SkXfermode::kSrc_Mode);
    resultImage->context()->drawBitmap(nativeImage->bitmap(), destRect.x(), destRect.y(), &paint);

    if (affectsTransparentPixels()) {
        IntRect fullRect = IntRect(IntPoint(), absolutePaintRect().size());
        resultImage->context()->clipOut(destRect);
        resultImage->context()->fillRect(fullRect, Color(rValues[0], gValues[0], bValues[0], aValues[0]));
    }
}

bool FEComponentTransfer::affectsTransparentPixels()
{
    double intercept = 0;
    switch (m_alphaFunc.type) {
    case FECOMPONENTTRANSFER_TYPE_UNKNOWN:
    case FECOMPONENTTRANSFER_TYPE_IDENTITY:
        break;
    case FECOMPONENTTRANSFER_TYPE_TABLE:
    case FECOMPONENTTRANSFER_TYPE_DISCRETE:
        if (m_alphaFunc.tableValues.size() > 0)
            intercept = m_alphaFunc.tableValues[0];
        break;
    case FECOMPONENTTRANSFER_TYPE_LINEAR:
        intercept = m_alphaFunc.intercept;
        break;
    case FECOMPONENTTRANSFER_TYPE_GAMMA:
        intercept = m_alphaFunc.offset;
        break;
    }
    return 255 * intercept >= 1;
}

PassRefPtr<SkImageFilter> FEComponentTransfer::createImageFilter(SkiaImageFilterBuilder* builder)
{
    RefPtr<SkImageFilter> input(builder->build(inputEffect(0), operatingColorSpace()));

    unsigned char rValues[256], gValues[256], bValues[256], aValues[256];
    getValues(rValues, gValues, bValues, aValues);

    SkAutoTUnref<SkColorFilter> colorFilter(SkTableColorFilter::CreateARGB(aValues, rValues, gValues, bValues));

    SkImageFilter::CropRect cropRect = getCropRect(builder->cropOffset());
    return adoptRef(SkColorFilterImageFilter::Create(colorFilter, input.get(), &cropRect));
}

void FEComponentTransfer::getValues(unsigned char rValues[256], unsigned char gValues[256], unsigned char bValues[256], unsigned char aValues[256])
{
    for (unsigned i = 0; i < 256; ++i)
        rValues[i] = gValues[i] = bValues[i] = aValues[i] = i;
    unsigned char* tables[] = { rValues, gValues, bValues, aValues };
    ComponentTransferFunction transferFunction[] = {m_redFunc, m_greenFunc, m_blueFunc, m_alphaFunc};
    TransferType callEffect[] = {identity, identity, table, discrete, linear, gamma};

    for (unsigned channel = 0; channel < 4; channel++) {
        ASSERT_WITH_SECURITY_IMPLICATION(static_cast<size_t>(transferFunction[channel].type) < WTF_ARRAY_LENGTH(callEffect));
        (*callEffect[transferFunction[channel].type])(tables[channel], transferFunction[channel]);
    }
}

static TextStream& operator<<(TextStream& ts, const ComponentTransferType& type)
{
    switch (type) {
    case FECOMPONENTTRANSFER_TYPE_UNKNOWN:
        ts << "UNKNOWN";
        break;
    case FECOMPONENTTRANSFER_TYPE_IDENTITY:
        ts << "IDENTITY";
        break;
    case FECOMPONENTTRANSFER_TYPE_TABLE:
        ts << "TABLE";
        break;
    case FECOMPONENTTRANSFER_TYPE_DISCRETE:
        ts << "DISCRETE";
        break;
    case FECOMPONENTTRANSFER_TYPE_LINEAR:
        ts << "LINEAR";
        break;
    case FECOMPONENTTRANSFER_TYPE_GAMMA:
        ts << "GAMMA";
        break;
    }
    return ts;
}

static TextStream& operator<<(TextStream& ts, const ComponentTransferFunction& function)
{
    ts << "type=\"" << function.type
       << "\" slope=\"" << function.slope
       << "\" intercept=\"" << function.intercept
       << "\" amplitude=\"" << function.amplitude
       << "\" exponent=\"" << function.exponent
       << "\" offset=\"" << function.offset << "\"";
    return ts;
}

TextStream& FEComponentTransfer::externalRepresentation(TextStream& ts, int indent) const
{
    writeIndent(ts, indent);
    ts << "[feComponentTransfer";
    FilterEffect::externalRepresentation(ts);
    ts << " \n";
    writeIndent(ts, indent + 2);
    ts << "{red: " << m_redFunc << "}\n";
    writeIndent(ts, indent + 2);
    ts << "{green: " << m_greenFunc << "}\n";
    writeIndent(ts, indent + 2);
    ts << "{blue: " << m_blueFunc << "}\n";
    writeIndent(ts, indent + 2);
    ts << "{alpha: " << m_alphaFunc << "}]\n";
    inputEffect(0)->externalRepresentation(ts, indent + 1);
    return ts;
}

} // namespace WebCore