Add image dump in PNG (#302)

This change adds support to dump image to PNG format, it relies on the
third party 'lodepng' library (zlib license).

This CL is based on Pull #301 by @hevrard.

6 files changed, 131 insertions, 7 deletions

diff --git a/samples/Android.mk b/samples/Android.mk
index 9d8033e..06f5fe9 100644
--- a/samples/Android.mk
+++ b/samples/Android.mk
@@ -22,11 +22,12 @@ LOCAL_SRC_FILES:= \
     config_helper.cc \
     config_helper_vulkan.cc \
     log.cc \
-    ppm.cc
+    ppm.cc \
+    png.cc
 LOCAL_C_INCLUDES := $(LOCAL_PATH)/.. $(LOCAL_PATH)/../include
 LOCAL_LDLIBS:=-landroid -lvulkan -llog
 LOCAL_CXXFLAGS:=-std=c++11 -fno-exceptions -fno-rtti -Werror -Wno-unknown-pragmas -DAMBER_ENGINE_VULKAN=1
-LOCAL_STATIC_LIBRARIES:=amber
+LOCAL_STATIC_LIBRARIES:=amber lodepng
 include $(BUILD_EXECUTABLE)
 
 include $(LOCAL_PATH)/../Android.mk
diff --git a/samples/CMakeLists.txt b/samples/CMakeLists.txt
index c71291a..77e1da7 100644
--- a/samples/CMakeLists.txt
+++ b/samples/CMakeLists.txt
@@ -19,10 +19,11 @@ set(AMBER_SOURCES
     config_helper.cc
     log.cc
     ppm.cc
+    png.cc
     ${CMAKE_BINARY_DIR}/src/build-versions.h.fake
 )
 
-set(AMBER_EXTRA_LIBS "")
+set(AMBER_EXTRA_LIBS "lodepng")
 
 if (${Vulkan_FOUND})
   set(AMBER_SOURCES ${AMBER_SOURCES} config_helper_vulkan.cc)
diff --git a/samples/amber.cc b/samples/amber.cc
index 33fcf70..012f273 100644
--- a/samples/amber.cc
+++ b/samples/amber.cc
@@ -24,6 +24,7 @@
 #include "amber/amber.h"
 #include "amber/recipe.h"
 #include "samples/config_helper.h"
+#include "samples/png.h"
 #include "samples/ppm.h"
 #include "src/build-versions.h"
 #include "src/make_unique.h"
@@ -56,7 +57,7 @@ const char kUsage[] = R"(Usage: amber [options] SCRIPT [SCRIPTS...]
   -s                        -- Print summary of pass/failure.
   -d                        -- Disable validation layers.
   -t <spirv_env>            -- The target SPIR-V environment. Defaults to SPV_ENV_UNIVERSAL_1_0.
-  -i <filename>             -- Write rendering to <filename> as a PPM image.
+  -i <filename>             -- Write rendering to <filename> as a PNG image if it ends with '.png', or as a PPM image otherwise.
   -b <filename>             -- Write contents of a UBO or SSBO to <filename>.
   -B [<desc set>:]<binding> -- Descriptor set and binding of buffer to write.
                                Default is [0:]0.
@@ -330,10 +331,19 @@ int main(int argc, const char** argv) {
 
     if (!options.image_filename.empty()) {
       std::string image;
+
+      auto pos = options.image_filename.find_last_of('.');
+      bool usePNG = pos != std::string::npos &&
+                    options.image_filename.substr(pos + 1) == "png";
       for (amber::BufferInfo buffer_info : amber_options.extractions) {
         if (buffer_info.buffer_name == "framebuffer") {
-          std::tie(result, image) = ppm::ConvertToPPM(
-              buffer_info.width, buffer_info.height, buffer_info.values);
+          if (usePNG) {
+            std::tie(result, image) = png::ConvertToPNG(
+                buffer_info.width, buffer_info.height, buffer_info.values);
+          } else {
+            std::tie(result, image) = ppm::ConvertToPPM(
+                buffer_info.width, buffer_info.height, buffer_info.values);
+          }
           break;
         }
       }
diff --git a/samples/png.cc b/samples/png.cc
new file mode 100644
index 0000000..79c6983
--- /dev/null
+++ b/samples/png.cc
@@ -0,0 +1,76 @@
+// Copyright 2019 The Amber Authors.
+//
+// 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 "samples/png.h"
+
+#include <cassert>
+
+#include "amber/result.h"
+#include "amber/value.h"
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wweak-vtables"
+#include "third_party/lodepng/lodepng.h"
+#pragma clang diagnostic pop
+
+namespace png {
+
+namespace {
+
+unsigned char byte0(uint32_t word) {
+  return static_cast<unsigned char>(word);
+}
+
+unsigned char byte1(uint32_t word) {
+  return static_cast<unsigned char>(word >> 8);
+}
+
+unsigned char byte2(uint32_t word) {
+  return static_cast<unsigned char>(word >> 16);
+}
+
+unsigned char byte3(uint32_t word) {
+  return static_cast<unsigned char>(word >> 24);
+}
+
+}  // namespace
+
+std::pair<amber::Result, std::string> ConvertToPNG(
+    uint32_t width,
+    uint32_t height,
+    const std::vector<amber::Value>& values) {
+  assert(values.size() == width * height);
+
+  std::vector<unsigned char> data;
+
+  // Prepare data as lodepng expects it
+  for (amber::Value value : values) {
+    const uint32_t pixel = value.AsUint32();
+    data.push_back(byte2(pixel));  // R
+    data.push_back(byte1(pixel));  // G
+    data.push_back(byte0(pixel));  // B
+    data.push_back(byte3(pixel));  // A
+  }
+
+  std::vector<unsigned char> png;
+  unsigned error = lodepng::encode(png, data, width, height);
+  if (error) {
+    return std::make_pair(amber::Result("lodepng::encode() returned non-zero"),
+                          nullptr);
+  }
+
+  return std::make_pair(amber::Result(), std::string(png.begin(), png.end()));
+}
+
+}  // namespace png
diff --git a/samples/png.h b/samples/png.h
new file mode 100644
index 0000000..2008e9e
--- /dev/null
+++ b/samples/png.h
@@ -0,0 +1,36 @@
+// Copyright 2019 The Amber Authors.
+//
+// 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.
+
+#ifndef SAMPLES_PNG_H_
+#define SAMPLES_PNG_H_
+
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "amber/amber.h"
+
+namespace png {
+
+/// Converts the image of dimensions |width| and |height| and with pixels stored
+/// in row-major order in |values| with format B8G8R8A8 into PNG format,
+/// returning the PNG binary as a string.
+std::pair<amber::Result, std::string> ConvertToPNG(
+    uint32_t width,
+    uint32_t height,
+    const std::vector<amber::Value>& values);
+
+}  // namespace png
+
+#endif  // SAMPLES_PNG_H_
diff --git a/samples/ppm.h b/samples/ppm.h
index 0eb1f8e..9b237f3 100644
--- a/samples/ppm.h
+++ b/samples/ppm.h
@@ -24,7 +24,7 @@
 namespace ppm {
 
 /// Converts the image of dimensions |width| and |height| and with pixels stored
-/// in row-major order in |values| with format R8G8B8A8 into PPM format,
+/// in row-major order in |values| with format B8G8R8A8 into PPM format,
 /// returning the PPM binary as a string.
 std::pair<amber::Result, std::string> ConvertToPPM(
     uint32_t width,