int guac_png_write()

in src/libguac/encode-png.c [269:404]

• 83 lines of code
• 13 McCabe index (conditional complexity)

int guac_png_write(guac_socket* socket, guac_stream* stream,
        cairo_surface_t* surface) {

    png_structp png;
    png_infop png_info;
    png_byte** png_rows;
    int bpp;

    int x, y;

    guac_png_write_state write_state;

    /* Get image surface properties and data */
    cairo_format_t format = cairo_image_surface_get_format(surface);
    int width = cairo_image_surface_get_width(surface);
    int height = cairo_image_surface_get_height(surface);
    int stride = cairo_image_surface_get_stride(surface);
    unsigned char* data = cairo_image_surface_get_data(surface);

    /* If not RGB24, use Cairo PNG writer */
    if (format != CAIRO_FORMAT_RGB24 || data == NULL)
        return guac_png_cairo_write(socket, stream, surface);

    /* Flush pending operations to surface */
    cairo_surface_flush(surface);

    /* Attempt to build palette */
    guac_palette* palette = guac_palette_alloc(surface);

    /* If not possible, resort to Cairo PNG writer */
    if (palette == NULL)
        return guac_png_cairo_write(socket, stream, surface);

    /* Calculate BPP from palette size */
    if      (palette->size <= 2)  bpp = 1;
    else if (palette->size <= 4)  bpp = 2;
    else if (palette->size <= 16) bpp = 4;
    else                          bpp = 8;

    /* Set up PNG writer */
    png = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    if (!png) {
        guac_palette_free(palette);
        guac_error = GUAC_STATUS_INTERNAL_ERROR;
        guac_error_message = "libpng failed to create write structure";
        return -1;
    }

    png_info = png_create_info_struct(png);
    if (!png_info) {
        png_destroy_write_struct(&png, NULL);
        guac_palette_free(palette);
        guac_error = GUAC_STATUS_INTERNAL_ERROR;
        guac_error_message = "libpng failed to create info structure";
        return -1;
    }

    /* Set error handler */
    if (setjmp(png_jmpbuf(png))) {
        png_destroy_write_struct(&png, &png_info);
        guac_palette_free(palette);
        guac_error = GUAC_STATUS_IO_ERROR;
        guac_error_message = "libpng output error";
        return -1;
    }

    /* Init write state */
    write_state.socket = socket;
    write_state.stream = stream;
    write_state.buffer_size = 0;

    /* Set up writer */
    png_set_write_fn(png, &write_state,
            guac_png_write_handler,
            guac_png_flush_handler);

    /* Copy data from surface into PNG data */
    png_rows = (png_byte**) guac_mem_alloc(sizeof(png_byte*), height);
    for (y=0; y<height; y++) {

        /* Allocate new PNG row */
        png_byte* row = (png_byte*) guac_mem_alloc(sizeof(png_byte), width);
        png_rows[y] = row;

        /* Copy data from surface into current row */
        for (x=0; x<width; x++) {

            /* Get pixel color */
            int color = ((uint32_t*) data)[x] & 0xFFFFFF;

            /* Set index in row */
            row[x] = guac_palette_find(palette, color);

        }

        /* Advance to next data row */
        data += stride;

    }

    /* Write image info */
    png_set_IHDR(
        png,
        png_info,
        width,
        height,
        bpp,
        PNG_COLOR_TYPE_PALETTE,
        PNG_INTERLACE_NONE,
        PNG_COMPRESSION_TYPE_DEFAULT,
        PNG_FILTER_TYPE_DEFAULT
    );

    /* Write palette */
    png_set_PLTE(png, png_info, palette->colors, palette->size);

    /* Write image */
    png_set_rows(png, png_info, png_rows);
    png_write_png(png, png_info, PNG_TRANSFORM_PACKING, NULL);

    /* Finish write */
    png_destroy_write_struct(&png, &png_info);

    /* Free palette */
    guac_palette_free(palette);

    /* Free PNG data */
    for (y=0; y<height; y++)
        guac_mem_free(png_rows[y]);
    guac_mem_free(png_rows);

    /* Ensure all data is written */
    guac_png_flush_data(&write_state);
    return 0;

}