webp.c

    }
    return 0;
}

static int apply_subtract_green_transform(WebPContext *s)
{
    int x, y;
    ImageContext *img = &s->image[IMAGE_ROLE_ARGB];

    for (y = 0; y < img->frame->height; y++) {
        for (x = 0; x < img->frame->width; x++) {
            uint8_t *p = GET_PIXEL(img->frame, x, y);
            p[1] += p[2];
            p[3] += p[2];
        }
    }
    return 0;
}

static int apply_color_indexing_transform(WebPContext *s)
{
    ImageContext *img;
    ImageContext *pal;
    int i, x, y;
    uint8_t *p, *pi;

    img = &s->image[IMAGE_ROLE_ARGB];
    pal = &s->image[IMAGE_ROLE_COLOR_INDEXING];

    if (pal->size_reduction > 0) {
        BitstreamContext bc_g;
        uint8_t *line;
        int pixel_bits = 8 >> pal->size_reduction;

        line = av_malloc(img->frame->linesize[0]);
        if (!line)
            return AVERROR(ENOMEM);

        for (y = 0; y < img->frame->height; y++) {
            p = GET_PIXEL(img->frame, 0, y);
            memcpy(line, p, img->frame->linesize[0]);
            bitstream_init(&bc_g, line, img->frame->linesize[0] * 8);
            bitstream_skip(&bc_g, 16);
            i = 0;
            for (x = 0; x < img->frame->width; x++) {
                p    = GET_PIXEL(img->frame, x, y);
                p[2] = bitstream_read(&bc_g, pixel_bits);
                i++;
                if (i == 1 << pal->size_reduction) {
                    bitstream_skip(&bc_g, 24);
                    i = 0;
                }
            }
        }
        av_free(line);
    }

    for (y = 0; y < img->frame->height; y++) {
        for (x = 0; x < img->frame->width; x++) {
            p = GET_PIXEL(img->frame, x, y);
            i = p[2];
            if (i >= pal->frame->width) {
                av_log(s->avctx, AV_LOG_ERROR, "invalid palette index %d\n", i);
                return AVERROR_INVALIDDATA;
            }
            pi = GET_PIXEL(pal->frame, i, 0);
            AV_COPY32(p, pi);
        }
    }

    return 0;
}

static int vp8_lossless_decode_frame(AVCodecContext *avctx, AVFrame *p,
                                     int *got_frame, uint8_t *data_start,
                                     unsigned int data_size, int is_alpha_chunk)
{
    WebPContext *s = avctx->priv_data;
    int w, h, ret, i, used;

    if (!is_alpha_chunk) {
        s->lossless = 1;
        avctx->pix_fmt = AV_PIX_FMT_ARGB;
    }

    ret = bitstream_init(&s->bc, data_start, data_size * 8);
    if (ret < 0)
        return ret;

    if (!is_alpha_chunk) {
        if (bitstream_read(&s->bc, 8) != 0x2F) {
            av_log(avctx, AV_LOG_ERROR, "Invalid WebP Lossless signature\n");
            return AVERROR_INVALIDDATA;
        }

        w = bitstream_read(&s->bc, 14) + 1;
        h = bitstream_read(&s->bc, 14) + 1;
        if (s->width && s->width != w) {
            av_log(avctx, AV_LOG_WARNING, "Width mismatch. %d != %d\n",
                   s->width, w);
        }
        s->width = w;
        if (s->height && s->height != h) {
            av_log(avctx, AV_LOG_WARNING, "Height mismatch. %d != %d\n",
                   s->width, w);
        }
        s->height = h;

        ret = ff_set_dimensions(avctx, s->width, s->height);
        if (ret < 0)
            return ret;

        s->has_alpha = bitstream_read_bit(&s->bc);

        if (bitstream_read(&s->bc, 3) != 0x0) {
            av_log(avctx, AV_LOG_ERROR, "Invalid WebP Lossless version\n");
            return AVERROR_INVALIDDATA;
        }
    } else {
        if (!s->width || !s->height)
            return AVERROR_BUG;
        w = s->width;
        h = s->height;
    }

    /* parse transformations */
    s->nb_transforms = 0;
    s->reduced_width = 0;
    used = 0;
    while (bitstream_read_bit(&s->bc)) {
        enum TransformType transform = bitstream_read(&s->bc, 2);
        s->transforms[s->nb_transforms++] = transform;
        if (used & (1 << transform)) {
            av_log(avctx, AV_LOG_ERROR, "Transform %d used more than once\n",
                   transform);
            ret = AVERROR_INVALIDDATA;
            goto free_and_return;
        }
        used |= (1 << transform);
        switch (transform) {
        case PREDICTOR_TRANSFORM:
            ret = parse_transform_predictor(s);
            break;
        case COLOR_TRANSFORM:
            ret = parse_transform_color(s);
            break;
        case COLOR_INDEXING_TRANSFORM:
            ret = parse_transform_color_indexing(s);
            break;
        }
        if (ret < 0)
            goto free_and_return;
    }

    /* decode primary image */
    s->image[IMAGE_ROLE_ARGB].frame = p;
    if (is_alpha_chunk)
        s->image[IMAGE_ROLE_ARGB].is_alpha_primary = 1;
    ret = decode_entropy_coded_image(s, IMAGE_ROLE_ARGB, w, h);
    if (ret < 0)
        goto free_and_return;

    /* apply transformations */
    for (i = s->nb_transforms - 1; i >= 0; i--) {
        switch (s->transforms[i]) {
        case PREDICTOR_TRANSFORM:
            ret = apply_predictor_transform(s);
            break;
        case COLOR_TRANSFORM:
            ret = apply_color_transform(s);
            break;
        case SUBTRACT_GREEN:
            ret = apply_subtract_green_transform(s);
            break;
        case COLOR_INDEXING_TRANSFORM:
            ret = apply_color_indexing_transform(s);
            break;
        }
        if (ret < 0)
            goto free_and_return;
    }

    *got_frame   = 1;
    p->pict_type = AV_PICTURE_TYPE_I;
    p->key_frame = 1;
    ret          = data_size;

free_and_return:
    for (i = 0; i < IMAGE_ROLE_NB; i++)
        image_ctx_free(&s->image[i]);

    return ret;
}

static void alpha_inverse_prediction(AVFrame *frame, enum AlphaFilter m)
{
    int x, y, ls;
    uint8_t *dec;

    ls = frame->linesize[3];

    /* filter first row using horizontal filter */
    dec = frame->data[3] + 1;
    for (x = 1; x < frame->width; x++, dec++)
        *dec += *(dec - 1);

    /* filter first column using vertical filter */
    dec = frame->data[3] + ls;
    for (y = 1; y < frame->height; y++, dec += ls)
        *dec += *(dec - ls);

    /* filter the rest using the specified filter */
    switch (m) {
    case ALPHA_FILTER_HORIZONTAL:
        for (y = 1; y < frame->height; y++) {
            dec = frame->data[3] + y * ls + 1;
            for (x = 1; x < frame->width; x++, dec++)
                *dec += *(dec - 1);
        }
        break;
    case ALPHA_FILTER_VERTICAL:
        for (y = 1; y < frame->height; y++) {
            dec = frame->data[3] + y * ls + 1;
            for (x = 1; x < frame->width; x++, dec++)
                *dec += *(dec - ls);
        }
        break;
    case ALPHA_FILTER_GRADIENT:
        for (y = 1; y < frame->height; y++) {
            dec = frame->data[3] + y * ls + 1;
            for (x = 1; x < frame->width; x++, dec++)
                dec[0] += av_clip_uint8(*(dec - 1) + *(dec - ls) - *(dec - ls - 1));
        }
        break;
    }
}

static int vp8_lossy_decode_alpha(AVCodecContext *avctx, AVFrame *p,
                                  uint8_t *data_start,
                                  unsigned int data_size)
{
    WebPContext *s = avctx->priv_data;
    int x, y, ret;

    if (s->alpha_compression == ALPHA_COMPRESSION_NONE) {
        GetByteContext gb;

        bytestream2_init(&gb, data_start, data_size);
        for (y = 0; y < s->height; y++)
            bytestream2_get_buffer(&gb, p->data[3] + p->linesize[3] * y,
                                   s->width);
    } else if (s->alpha_compression == ALPHA_COMPRESSION_VP8L) {
        uint8_t *ap, *pp;
        int alpha_got_frame = 0;

        s->alpha_frame = av_frame_alloc();
        if (!s->alpha_frame)
            return AVERROR(ENOMEM);

        ret = vp8_lossless_decode_frame(avctx, s->alpha_frame, &alpha_got_frame,
                                        data_start, data_size, 1);
        if (ret < 0) {
            av_frame_free(&s->alpha_frame);
            return ret;
        }
        if (!alpha_got_frame) {
            av_frame_free(&s->alpha_frame);
            return AVERROR_INVALIDDATA;
        }

        /* copy green component of alpha image to alpha plane of primary image */
        for (y = 0; y < s->height; y++) {
            ap = GET_PIXEL(s->alpha_frame, 0, y) + 2;
            pp = p->data[3] + p->linesize[3] * y;
            for (x = 0; x < s->width; x++) {
                *pp = *ap;
                pp++;
                ap += 4;
            }
        }
        av_frame_free(&s->alpha_frame);
    }

    /* apply alpha filtering */
    if (s->alpha_filter)
        alpha_inverse_prediction(p, s->alpha_filter);

    return 0;
}

static int vp8_lossy_decode_frame(AVCodecContext *avctx, AVFrame *p,
                                  int *got_frame, uint8_t *data_start,
                                  unsigned int data_size)
{
    WebPContext *s = avctx->priv_data;
    AVPacket pkt;
    int ret;

    if (!s->initialized) {
        ff_vp8_decode_init(avctx);
        s->initialized = 1;
        if (s->has_alpha)
            avctx->pix_fmt = AV_PIX_FMT_YUVA420P;
    }
    s->lossless = 0;

    if (data_size > INT_MAX) {
        av_log(avctx, AV_LOG_ERROR, "unsupported chunk size\n");
        return AVERROR_PATCHWELCOME;
    }

    av_init_packet(&pkt);
    pkt.data = data_start;
    pkt.size = data_size;

    ret = ff_vp8_decode_frame(avctx, p, got_frame, &pkt);
    if (s->has_alpha) {
        ret = vp8_lossy_decode_alpha(avctx, p, s->alpha_data,
                                     s->alpha_data_size);
        if (ret < 0)
            return ret;
    }
    return ret;
}

static int webp_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
                             AVPacket *avpkt)
{
    AVFrame * const p = data;
    WebPContext *s = avctx->priv_data;
    GetByteContext gb;
    int ret;
    uint32_t chunk_type, chunk_size;
    int vp8x_flags = 0;

    s->avctx     = avctx;
    s->width     = 0;
    s->height    = 0;
    *got_frame   = 0;
    s->has_alpha = 0;
    bytestream2_init(&gb, avpkt->data, avpkt->size);

    if (bytestream2_get_bytes_left(&gb) < 12)
        return AVERROR_INVALIDDATA;

    if (bytestream2_get_le32(&gb) != MKTAG('R', 'I', 'F', 'F')) {
        av_log(avctx, AV_LOG_ERROR, "missing RIFF tag\n");
        return AVERROR_INVALIDDATA;
    }

    chunk_size = bytestream2_get_le32(&gb);
    if (bytestream2_get_bytes_left(&gb) < chunk_size)
        return AVERROR_INVALIDDATA;

    if (bytestream2_get_le32(&gb) != MKTAG('W', 'E', 'B', 'P')) {
        av_log(avctx, AV_LOG_ERROR, "missing WEBP tag\n");
        return AVERROR_INVALIDDATA;
    }

    while (bytestream2_get_bytes_left(&gb) > 8) {
        char chunk_str[5] = { 0 };

        chunk_type = bytestream2_get_le32(&gb);
        chunk_size = bytestream2_get_le32(&gb);
        if (chunk_size == UINT32_MAX)
            return AVERROR_INVALIDDATA;
        chunk_size += chunk_size & 1;

        if (bytestream2_get_bytes_left(&gb) < chunk_size)
            return AVERROR_INVALIDDATA;

        switch (chunk_type) {
        case MKTAG('V', 'P', '8', ' '):
            if (!*got_frame) {
                ret = vp8_lossy_decode_frame(avctx, p, got_frame,
                                             avpkt->data + bytestream2_tell(&gb),
                                             chunk_size);
                if (ret < 0)
                    return ret;
            }
            bytestream2_skip(&gb, chunk_size);
            break;
        case MKTAG('V', 'P', '8', 'L'):
            if (!*got_frame) {
                ret = vp8_lossless_decode_frame(avctx, p, got_frame,
                                                avpkt->data + bytestream2_tell(&gb),
                                                chunk_size, 0);
                if (ret < 0)
                    return ret;
            }
            bytestream2_skip(&gb, chunk_size);
            break;
        case MKTAG('V', 'P', '8', 'X'):
            vp8x_flags = bytestream2_get_byte(&gb);
            bytestream2_skip(&gb, 3);
            s->width  = bytestream2_get_le24(&gb) + 1;
            s->height = bytestream2_get_le24(&gb) + 1;
            ret = av_image_check_size(s->width, s->height, 0, avctx);
            if (ret < 0)
                return ret;
            break;
        case MKTAG('A', 'L', 'P', 'H'): {
            int alpha_header, filter_m, compression;

            if (!(vp8x_flags & VP8X_FLAG_ALPHA)) {
                av_log(avctx, AV_LOG_WARNING,
                       "ALPHA chunk present, but alpha bit not set in the "
                       "VP8X header\n");
            }
            if (chunk_size == 0) {
                av_log(avctx, AV_LOG_ERROR, "invalid ALPHA chunk size\n");
                return AVERROR_INVALIDDATA;
            }
            alpha_header       = bytestream2_get_byte(&gb);
            s->alpha_data      = avpkt->data + bytestream2_tell(&gb);
            s->alpha_data_size = chunk_size - 1;
            bytestream2_skip(&gb, s->alpha_data_size);

            filter_m    = (alpha_header >> 2) & 0x03;
            compression =  alpha_header       & 0x03;

            if (compression > ALPHA_COMPRESSION_VP8L) {
                av_log(avctx, AV_LOG_VERBOSE,
                       "skipping unsupported ALPHA chunk\n");
            } else {
                s->has_alpha         = 1;
                s->alpha_compression = compression;
                s->alpha_filter      = filter_m;
            }

            break;
        }
        case MKTAG('I', 'C', 'C', 'P'):
        case MKTAG('A', 'N', 'I', 'M'):
        case MKTAG('A', 'N', 'M', 'F'):
        case MKTAG('E', 'X', 'I', 'F'):
        case MKTAG('X', 'M', 'P', ' '):
            AV_WL32(chunk_str, chunk_type);
            av_log(avctx, AV_LOG_VERBOSE, "skipping unsupported chunk: %s\n",
                   chunk_str);
            bytestream2_skip(&gb, chunk_size);
            break;
        default:
            AV_WL32(chunk_str, chunk_type);
            av_log(avctx, AV_LOG_VERBOSE, "skipping unknown chunk: %s\n",
                   chunk_str);
            bytestream2_skip(&gb, chunk_size);
            break;
        }
    }

    if (!*got_frame) {
        av_log(avctx, AV_LOG_ERROR, "image data not found\n");
        return AVERROR_INVALIDDATA;
    }

    return avpkt->size;
}

static av_cold int webp_decode_close(AVCodecContext *avctx)
{
    WebPContext *s = avctx->priv_data;

    if (s->initialized)
        return ff_vp8_decode_free(avctx);

    return 0;
}

AVCodec ff_webp_decoder = {
    .name           = "webp",
    .long_name      = NULL_IF_CONFIG_SMALL("WebP image"),
    .type           = AVMEDIA_TYPE_VIDEO,
    .id             = AV_CODEC_ID_WEBP,
    .priv_data_size = sizeof(WebPContext),
    .decode         = webp_decode_frame,
    .close          = webp_decode_close,
    .capabilities   = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_FRAME_THREADS,
};