src/images/SkWebpEncoder.cpp

/*
 * Copyright 2010 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "src/images/SkImageEncoderPriv.h"

#ifdef SK_ENCODE_WEBP

#include "include/core/SkBitmap.h"
#include "include/core/SkStream.h"
#include "include/core/SkUnPreMultiply.h"
#include "include/encode/SkWebpEncoder.h"
#include "include/private/SkColorData.h"
#include "include/private/SkImageInfoPriv.h"
#include "include/private/SkTemplates.h"
#include "src/images/SkImageEncoderFns.h"
#include "src/utils/SkUTF.h"

// A WebP encoder only, on top of (subset of) libwebp
// For more information on WebP image format, and libwebp library, see:
//   http://code.google.com/speed/webp/
//   http://www.webmproject.org/code/#libwebp_webp_image_decoder_library
//   http://review.webmproject.org/gitweb?p=libwebp.git

#include <stdio.h>
extern "C" {
// If moving libwebp out of skia source tree, path for webp headers must be
// updated accordingly. Here, we enforce using local copy in webp sub-directory.
#include "webp/encode.h"
#include "webp/mux.h"
}

static int stream_writer(const uint8_t* data, size_t data_size,
                         const WebPPicture* const picture) {
  SkWStream* const stream = (SkWStream*)picture->custom_ptr;
  return stream->write(data, data_size) ? 1 : 0;
}

using WebPPictureImportProc = int (*) (WebPPicture* picture, const uint8_t* pixels, int stride);

bool SkWebpEncoder::Encode(SkWStream* stream, const SkPixmap& pixmap, const Options& opts) {
    if (!SkPixmapIsValid(pixmap)) {
        return false;
    }

    if (SkColorTypeIsAlphaOnly(pixmap.colorType())) {
        // Maintain the existing behavior of not supporting encoding alpha-only images.
        // TODO: Support encoding alpha only to an image with alpha but no color?
        return false;
    }

    if (nullptr == pixmap.addr()) {
        return false;
    }

    WebPConfig webp_config;
    if (!WebPConfigPreset(&webp_config, WEBP_PRESET_DEFAULT, opts.fQuality)) {
        return false;
    }

    WebPPicture pic;
    WebPPictureInit(&pic);
    SkAutoTCallVProc<WebPPicture, WebPPictureFree> autoPic(&pic);
    pic.width = pixmap.width();
    pic.height = pixmap.height();
    pic.writer = stream_writer;

    // Set compression, method, and pixel format.
    // libwebp recommends using BGRA for lossless and YUV for lossy.
    // The choices of |webp_config.method| currently just match Chrome's defaults.  We
    // could potentially expose this decision to the client.
    if (Compression::kLossy == opts.fCompression) {
        webp_config.lossless = 0;
#ifndef SK_WEBP_ENCODER_USE_DEFAULT_METHOD
        webp_config.method = 3;
#endif
        pic.use_argb = 0;
    } else {
        webp_config.lossless = 1;
        webp_config.method = 0;
        pic.use_argb = 1;
    }

    // If there is no need to embed an ICC profile, we write directly to the input stream.
    // Otherwise, we will first encode to |tmp| and use a mux to add the ICC chunk.  libwebp
    // forces us to have an encoded image before we can add a profile.
    sk_sp<SkData> icc = icc_from_color_space(pixmap.info());
    SkDynamicMemoryWStream tmp;
    pic.custom_ptr = icc ? (void*)&tmp : (void*)stream;

    {
        const SkColorType ct = pixmap.colorType();
        const bool premul = pixmap.alphaType() == kPremul_SkAlphaType;

        SkBitmap tmpBm;
        WebPPictureImportProc importProc = nullptr;
        const SkPixmap* src = &pixmap;
        if      (           ct ==  kRGB_888x_SkColorType) { importProc = WebPPictureImportRGBX; }
        else if (!premul && ct == kRGBA_8888_SkColorType) { importProc = WebPPictureImportRGBA; }
#ifdef WebPPictureImportBGRA
        else if (!premul && ct == kBGRA_8888_SkColorType) { importProc = WebPPictureImportBGRA; }
#endif
        else {
            importProc = WebPPictureImportRGBA;
            auto info = pixmap.info().makeColorType(kRGBA_8888_SkColorType)
                                     .makeAlphaType(kUnpremul_SkAlphaType);
            if (!tmpBm.tryAllocPixels(info)
                    || !pixmap.readPixels(tmpBm.info(), tmpBm.getPixels(), tmpBm.rowBytes())) {
                return false;
            }
            src = &tmpBm.pixmap();
        }

        if (!importProc(&pic, reinterpret_cast<const uint8_t*>(src->addr()), src->rowBytes())) {
            return false;
        }
    }

    if (!WebPEncode(&webp_config, &pic)) {
        return false;
    }

    if (icc) {
        sk_sp<SkData> encodedData = tmp.detachAsData();
        WebPData encoded = { encodedData->bytes(), encodedData->size() };
        WebPData iccChunk = { icc->bytes(), icc->size() };

        SkAutoTCallVProc<WebPMux, WebPMuxDelete> mux(WebPMuxNew());
        if (WEBP_MUX_OK != WebPMuxSetImage(mux, &encoded, 0)) {
            return false;
        }

        if (WEBP_MUX_OK != WebPMuxSetChunk(mux, "ICCP", &iccChunk, 0)) {
            return false;
        }

        WebPData assembled;
        if (WEBP_MUX_OK != WebPMuxAssemble(mux, &assembled)) {
            return false;
        }

        stream->write(assembled.bytes, assembled.size);
        WebPDataClear(&assembled);
    }

    return true;
}

#endif