Add Jpeg frame writer for test support.

webrtc/test/testsupport/jpeg_frame_writer.cc

+/*
+ *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include <stdio.h>
+
+
+#include "webrtc/common_types.h"
+#include "webrtc/common_video/libyuv/include/webrtc_libyuv.h"
+#include "webrtc/rtc_base/checks.h"
+#include "webrtc/test/testsupport/frame_writer.h"
+
+extern "C" {
+#if defined(USE_SYSTEM_LIBJPEG)
+#include <jpeglib.h>
+#elif defined(USE_LIBJPEG_TURBO)
+#include "third_party/libjpeg_turbo/jpeglib.h"
+#else
+#include "third_party/libjpeg/jpeglib.h"
+#endif
+}
+
+namespace webrtc {
+namespace test {
+
+JpegFrameWriter::JpegFrameWriter(std::string output_filename)
+    : frame_written_(false),
+      output_filename_(output_filename),
+      output_file_(nullptr) {}
+
+bool JpegFrameWriter::WriteFrame(const VideoFrame& input_frame, int quality) {
+  RTC_CHECK(!frame_written_) << "Only s single frame can be saved to Jpeg.";

[sprang_webrtc, 2017/08/17 15:27:50]

s? You mean "a"?

[ilnik, 2017/08/18 08:42:05]

Yep, a typo. Thanks.

+  const int kColorPlanes = 3;  // R, G and B.
+  size_t rgb_len = input_frame.height() * input_frame.width() * kColorPlanes;
+  std::unique_ptr<uint8_t> rgb_buf(new uint8_t[rgb_len]);

[sprang_webrtc, 2017/08/17 15:27:50]

Hm, shouldn't this be a std::unique_ptr<uint8_t[]> ?

[ilnik, 2017/08/18 08:42:05]

Done.

+
+  // kRGB24 actually corresponds to FourCC 24BG which is 24-bit BGR.
+  if (ConvertFromI420(input_frame, VideoType::kRGB24, 0, rgb_buf.get()) < 0) {
+    fprintf(stderr, "Could not convert input frame to RGB.\n");

[sprang_webrtc, 2017/08/17 15:27:50]

Use LOG macros

[ilnik, 2017/08/18 08:42:05]

Done.

+    return false;
+  }
+  output_file_ = fopen(output_filename_.c_str(), "wb");
+  if (!output_file_) {
+    fprintf(stderr, "Couldn't open file to write jpeg frame to: %s\n",
+            output_filename_.c_str());
+    return false;
+  }
+
+  // Invoking LIBJPEG
+  struct jpeg_compress_struct cinfo;
+  struct jpeg_error_mgr jerr;
+  JSAMPROW row_pointer[1];
+  cinfo.err = jpeg_std_error(&jerr);
+  jpeg_create_compress(&cinfo);
+
+  jpeg_stdio_dest(&cinfo, output_file_);

[sprang_webrtc, 2017/08/17 15:27:50]

Would it be possible to write to a buffer instead, and write to file using
FileWrapper?
Would like avoid direct access to os primitives.

[ilnik, 2017/08/18 08:42:05]

It's problematic. Outputting to memory is available in the latest versions of
libjpeg, but not in the one in third_party. There's a workaround, there we write
our own output wrapper with special libjpeg interface, but I think it's an
overkill here. 

[sprang_webrtc, 2017/08/18 08:48:03]

Fair enough, let's leave it as is.

+
+  cinfo.image_width = input_frame.width();
+  cinfo.image_height = input_frame.height();
+  cinfo.input_components = kColorPlanes;
+  cinfo.in_color_space = JCS_EXT_BGR;
+  jpeg_set_defaults(&cinfo);
+  jpeg_set_quality(&cinfo, quality, TRUE);
+
+  jpeg_start_compress(&cinfo, TRUE);
+  int row_stride = input_frame.width() * kColorPlanes;
+  while (cinfo.next_scanline < cinfo.image_height) {
+    row_pointer[0] = &rgb_buf.get()[cinfo.next_scanline * row_stride];
+    (void)jpeg_write_scanlines(&cinfo, row_pointer, 1);

[sprang_webrtc, 2017/08/17 15:27:50]

why the (void) ?

[ilnik, 2017/08/18 08:42:04]

Came from the example code. Probably has to do something with warnings. But it's
not needed here. Removed.

+  }
+
+  jpeg_finish_compress(&cinfo);
+  jpeg_destroy_compress(&cinfo);
+  fclose(output_file_);
+
+  frame_written_ = true;
+  return true;
+}
+
+}  // namespace test
+}  // namespace webrtc