src/images/SkWEBPImageEncoder.cpp

/*
 * Copyright 2010, The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "SkImageEncoderPriv.h"

#ifdef SK_HAS_WEBP_LIBRARY

#include "SkBitmap.h"
#include "SkColorPriv.h"
#include "SkStream.h"
#include "SkTemplates.h"
#include "SkUnPreMultiply.h"
#include "SkUtils.h"
#include "transform_scanline.h"

// A WebP decoder 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"
}

static transform_scanline_proc choose_proc(const SkImageInfo& info, int* bpp) {
    switch (info.colorType()) {
        case kRGBA_8888_SkColorType:
            switch (info.alphaType()) {
                case kOpaque_SkAlphaType:
                    *bpp = 3;
                    return transform_scanline_RGBX;
                case kUnpremul_SkAlphaType:
                    *bpp = 4;
                    return transform_scanline_memcpy;
                case kPremul_SkAlphaType:
                    *bpp = 4;
                    return transform_scanline_rgbA;
                default:
                    return nullptr;
            }
        case kBGRA_8888_SkColorType:
            switch (info.alphaType()) {
                case kOpaque_SkAlphaType:
                    *bpp = 3;
                    return transform_scanline_BGRX;
                case kUnpremul_SkAlphaType:
                    *bpp = 4;
                    return transform_scanline_BGRA;
                case kPremul_SkAlphaType:
                    *bpp = 4;
                    return transform_scanline_bgrA;
                default:
                    return nullptr;
            }
        case kRGB_565_SkColorType:
            *bpp = 3;
            return transform_scanline_565;
        case kARGB_4444_SkColorType:
            switch (info.alphaType()) {
                case kOpaque_SkAlphaType:
                    *bpp = 3;
                    return transform_scanline_444;
                case kPremul_SkAlphaType:
                    *bpp = 4;
                    return transform_scanline_4444;
                default:
                    return nullptr;
            }
        case kIndex_8_SkColorType:
            switch (info.alphaType()) {
                case kOpaque_SkAlphaType:
                    *bpp = 3;
                    return transform_scanline_index8_opaque;
                case kUnpremul_SkAlphaType:
                case kPremul_SkAlphaType:
                    // If the color table is premultiplied, we'll fix it before calling the
                    // scanline proc.
                    *bpp = 4;
                    return transform_scanline_index8_unpremul;
                default:
                    return nullptr;
            }
        case kGray_8_SkColorType:
            *bpp = 3;
            return transform_scanline_gray;
        default:
            return nullptr;
    }
}

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;
}

bool SkEncodeImageAsWEBP(SkWStream* stream, const SkPixmap& pixmap, int quality) {
    int bpp = -1;
    const transform_scanline_proc proc = choose_proc(pixmap.info(), &bpp);
    if (!proc) {
        return false;
    }
    SkASSERT(-1 != bpp);

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

    const SkPMColor* colors = nullptr;
    SkPMColor storage[256];
    if (kIndex_8_SkColorType == pixmap.colorType()) {
        if (!pixmap.ctable()) {
            return false;
        }

        colors = pixmap.ctable()->readColors();
        if (kPremul_SkAlphaType == pixmap.alphaType()) {
            transform_scanline_rgbA((char*) storage, (const char*) colors, pixmap.ctable()->count(),
                                    4, nullptr);
            colors = storage;
        }
    }

    WebPConfig webp_config;
    if (!WebPConfigPreset(&webp_config, WEBP_PRESET_DEFAULT, (float) quality)) {
        return false;
    }

    WebPPicture pic;
    WebPPictureInit(&pic);
    pic.width = pixmap.width();
    pic.height = pixmap.height();
    pic.writer = stream_writer;
    pic.custom_ptr = (void*)stream;

    const uint8_t* src = (uint8_t*)pixmap.addr();
    const int rgbStride = pic.width * bpp;
    const size_t rowBytes = pixmap.rowBytes();

    // Import (for each scanline) the bit-map image (in appropriate color-space)
    // to RGB color space.
    std::unique_ptr<uint8_t[]> rgb(new uint8_t[rgbStride * pic.height]);
    for (int y = 0; y < pic.height; ++y) {
        proc((char*) &rgb[y * rgbStride], (const char*) &src[y * rowBytes], pic.width, bpp, colors);
    }

    bool ok;
    if (bpp == 3) {
        ok = SkToBool(WebPPictureImportRGB(&pic, &rgb[0], rgbStride));
    } else {
        ok = SkToBool(WebPPictureImportRGBA(&pic, &rgb[0], rgbStride));
    }

    ok = ok && WebPEncode(&webp_config, &pic);
    WebPPictureFree(&pic);

    return ok;
}
#endif