+ add webp writing support

include/mapnik/webp_io.hpp

@@ -0,0 +1,108 @@
+/*****************************************************************************
+ *
+ * This file is part of Mapnik (c++ mapping toolkit)
+ *
+ * Copyright (C) 2013 Artem Pavlenko
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ *****************************************************************************/
+
+#ifndef MAPNIK_WEBP_IO_HPP
+#define MAPNIK_WEBP_IO_HPP
+
+#include <webp/encode.h>
+
+#include <ostream>
+#include <sstream>
+#include <stdexcept>
+
+
+namespace mapnik {
+
+template <typename T>
+int webp_stream_write(const uint8_t* data, size_t data_size, const WebPPicture* picture)
+{
+    T* out = static_cast<T*>(picture->custom_ptr);
+    out->write(reinterpret_cast<const char*>(data), data_size);
+    return true;
+}
+
+std::string webp_encoding_error(WebPEncodingError error) {
+    std::ostringstream os;
+    switch (error) {
+        case VP8_ENC_ERROR_OUT_OF_MEMORY: os << "memory error allocating objects"; break;
+        case VP8_ENC_ERROR_BITSTREAM_OUT_OF_MEMORY: os << "memory error while flushing bits"; break;
+        case VP8_ENC_ERROR_NULL_PARAMETER: os << "a pointer parameter is NULL"; break;
+        case VP8_ENC_ERROR_INVALID_CONFIGURATION: os << "configuration is invalid"; break;
+        case VP8_ENC_ERROR_BAD_DIMENSION: os << "picture has invalid width/height"; break;
+        case VP8_ENC_ERROR_PARTITION0_OVERFLOW: os << "partition is bigger than 512k"; break;
+        case VP8_ENC_ERROR_PARTITION_OVERFLOW: os << "partition is bigger than 16M"; break;
+        case VP8_ENC_ERROR_BAD_WRITE: os << "error while flushing bytes"; break;
+        case VP8_ENC_ERROR_FILE_TOO_BIG: os << "file is bigger than 4G"; break;
+        default: os << "unknown error (" << error << ")"; break;
+    }
+    os << " during encoding";
+    return os.str();
+}
+
+template <typename T1, typename T2>
+void save_as_webp(T1& file, int quality, int compression, T2 const& image)
+{
+    WebPConfig config;
+    if (!WebPConfigPreset(&config, WEBP_PRESET_DEFAULT, quality))
+    {
+        throw std::runtime_error("version mismatch");
+    }
+
+    // Add additional tuning
+    if (compression >= 0) config.method = compression;
+
+    bool valid = WebPValidateConfig(&config);
+    if (!valid) {
+        throw std::runtime_error("Invalid configuration");
+    }
+
+    WebPPicture pic;
+    if (!WebPPictureInit(&pic))
+    {
+        throw std::runtime_error("version mismatch");
+    }
+    pic.width = image.width();
+    pic.height = image.height();
+    if (!WebPPictureAlloc(&pic))
+    {
+        throw std::runtime_error("memory error");
+    }
+
+    int stride = sizeof(typename T2::pixel_type) * image.width();
+    uint8_t const* bytes = reinterpret_cast<uint8_t const*>(image.getBytes());
+    int ok = WebPPictureImportRGBA(&pic, bytes, stride);
+
+    pic.writer = webp_stream_write<T1>;
+    pic.custom_ptr = &file;
+
+    ok = WebPEncode(&config, &pic);
+    WebPPictureFree(&pic);
+    if (!ok)
+    {
+        throw std::runtime_error(webp_encoding_error(pic.error_code));
+    }
+
+    file.flush();
+}
+}
+
+#endif // MAPNIK_WEBP_IO_HPP