1 files changed, 80 insertions, 0 deletions
diff --git a/src/webp.cc b/src/webp.cc
new file mode 100644
index 0000000..f2741e6
--- /dev/null
+++ b/src/webp.cc
@@ -0,0 +1,80 @@
+// Copyright 2021 Benjamin Barenblat
+//
+// 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
+//
+//     https://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 "src/webp.h"
+
+#include <stddef.h>
+#include <stdint.h>
+#include <webp/decode.h>
+
+#include <new>
+#include <stdexcept>
+#include <vector>
+
+#include "third_party/abseil/absl/strings/str_cat.h"
+#include "third_party/abseil/absl/strings/string_view.h"
+#include "third_party/abseil/absl/types/span.h"
+
+namespace glplanet {
+
+std::vector<uint8_t> DecodeWebp(absl::Span<const uint8_t> webp, int x, int y,
+                                int width, int height) {
+  size_t bytes = 3 * width * height;
+  std::vector<uint8_t> decoded(bytes, '\0');
+
+  WebPDecoderConfig config;
+  if (!WebPInitDecoderConfig(&config)) {
+    throw std::runtime_error("failed to initialize WebP decoder");
+  }
+
+  config.options.use_cropping = 1;
+  config.options.crop_left = x;
+  config.options.crop_top = y;
+  config.options.crop_width = width;
+  config.options.crop_height = height;
+
+  config.output.colorspace = MODE_RGB;
+  config.output.is_external_memory = 1;
+  config.output.u.RGBA.rgba = decoded.data();
+  config.output.u.RGBA.stride = 3 * width;
+  config.output.u.RGBA.size = bytes;
+
+  int error = WebPDecode(webp.data(), webp.size(), &config);
+  if (error != VP8_STATUS_OK) {
+    static constexpr absl::string_view error_prefix = "failed to decode WebP: ";
+    switch (error) {
+      case VP8_STATUS_OUT_OF_MEMORY:
+        throw std::bad_alloc();
+      case VP8_STATUS_INVALID_PARAM:
+        throw std::invalid_argument(
+            absl::StrCat(error_prefix, "invalid parameter"));
+      case VP8_STATUS_BITSTREAM_ERROR:
+        throw std::runtime_error(absl::StrCat(error_prefix, "bitstream error"));
+      case VP8_STATUS_UNSUPPORTED_FEATURE:
+        throw std::runtime_error(
+            absl::StrCat(error_prefix, "unsupported feature"));
+      case VP8_STATUS_SUSPENDED:
+        throw std::runtime_error(absl::StrCat(error_prefix, "suspended"));
+      case VP8_STATUS_USER_ABORT:
+        throw std::runtime_error(absl::StrCat(error_prefix, "aborted"));
+      case VP8_STATUS_NOT_ENOUGH_DATA:
+        throw std::runtime_error(absl::StrCat(error_prefix, "not enough data"));
+      default:
+        throw std::runtime_error(absl::StrCat(error_prefix, "unknown error"));
+    }
+  }
+  return decoded;
+}
+
+}  // namespace glplanet