Convert png from 16-bit grayscale to grayscale-alpha in RosCompressedStreamer.

Author: patrickcjh

CMakeLists.txt

@@ -49,6 +49,7 @@ add_executable(${PROJECT_NAME}
   src/ros_compressed_streamer.cpp
   src/jpeg_streamers.cpp
   src/png_streamers.cpp
+  src/crc32.cpp
 )
 
 ## Specify libraries to link a library or executable target against

include/web_video_server/crc32.h

@@ -0,0 +1,12 @@
+#ifndef CRC32_H_
+#define CRC32_H_
+
+#include <stdint.h>
+
+namespace web_video_server
+{
+uint32_t updateCrc32(uint32_t crc, const uint8_t* buf, uint32_t len);
+uint32_t crc32(const uint8_t* buf, uint32_t len);
+}
+
+#endif

include/web_video_server/ros_compressed_streamer.h

@@ -22,6 +22,7 @@ class RosCompressedStreamer : public ImageStreamer
 
 protected:
   virtual void sendImage(const sensor_msgs::CompressedImageConstPtr &msg, const ros::Time &time);
+  virtual void convertGrayscale16toGrayscaleAlpha(const sensor_msgs::CompressedImageConstPtr &msg);
 
 private:
   void imageCallback(const sensor_msgs::CompressedImageConstPtr &msg);

src/crc32.cpp

@@ -0,0 +1,88 @@
+#include "web_video_server/crc32.h"
+
+namespace web_video_server
+{
+
+const uint32_t CRC32_TABLE[256] =
+{
+  0x00000000, 0x77073096, 0xee0e612c, 0x990951ba,
+  0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
+  0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
+  0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
+  0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
+  0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
+  0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,
+  0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
+  0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
+  0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
+  0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940,
+  0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
+  0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116,
+  0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
+  0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
+  0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
+  0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a,
+  0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
+  0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818,
+  0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
+  0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
+  0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
+  0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c,
+  0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
+  0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
+  0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
+  0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
+  0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
+  0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086,
+  0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
+  0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4,
+  0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
+  0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
+  0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
+  0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
+  0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
+  0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe,
+  0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
+  0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
+  0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
+  0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252,
+  0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
+  0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60,
+  0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
+  0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
+  0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
+  0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04,
+  0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
+  0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a,
+  0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
+  0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
+  0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
+  0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e,
+  0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
+  0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
+  0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
+  0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
+  0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
+  0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0,
+  0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
+  0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6,
+  0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
+  0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
+  0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
+};
+
+uint32_t updateCrc32(uint32_t crc, const uint8_t* buf, uint32_t len)
+{
+  while (len--)
+  {
+    crc = CRC32_TABLE[(crc ^ *buf++) & 0xff] ^ (crc >> 8);
+  }
+  return crc;
+}
+
+uint32_t crc32(const uint8_t* buf, uint32_t len)
+{
+  return ~updateCrc32(0xffffffff, buf, len);
+}
+
+}

src/ros_compressed_streamer.cpp

@@ -1,4 +1,5 @@
 #include "web_video_server/ros_compressed_streamer.h"
+#include "web_video_server/crc32.h"
 
 namespace web_video_server
 {
@@ -41,6 +42,7 @@ void RosCompressedStreamer::sendImage(const sensor_msgs::CompressedImageConstPtr
     }
     else if(msg->format.find("png") != std::string::npos) {
       content_type = "image/png";
+      convertGrayscale16toGrayscaleAlpha(msg);
     }
     else {
       ROS_WARN_STREAM("Unknown ROS compressed image format: " << msg->format);
@@ -70,6 +72,34 @@ void RosCompressedStreamer::sendImage(const sensor_msgs::CompressedImageConstPtr
   }
 }
 
+void RosCompressedStreamer::convertGrayscale16toGrayscaleAlpha(const sensor_msgs::CompressedImageConstPtr &msg)
+{
+  static const uint8_t PNG_MAGIC_BYTES_AND_IHDR[16] = {
+    0x89, 'P', 'N', 'G', '\r', '\n', 0x1A, '\n',
+    '\0', '\0', '\0', '\r', 'I', 'H', 'D', 'R',
+  };
+  const std::vector<uint8_t>& data = msg->data;
+  if (data.size() <= 33 || memcmp(&data[0], PNG_MAGIC_BYTES_AND_IHDR, 16))
+  {
+    return;
+  }
+
+  static const uint8_t GRAYSCALE16[2] = {16, 0};
+  static const uint8_t GRAYSCALE_ALPHA[2] = {8, 4};
+
+  // check if 16-bit grayscale
+  if (memcmp(&data[0x18], GRAYSCALE16, 2) == 0)
+  {
+    uint32_t crc = 0xffffffff;
+    crc = updateCrc32(crc, &data[0x0C], 12);
+    crc = updateCrc32(crc, GRAYSCALE_ALPHA, 2);
+    crc = updateCrc32(crc, &data[0x1A], 3);
+    crc = ~crc;
+
+    *reinterpret_cast<uint32_t*>(const_cast<uint8_t*>(&data[0x1D])) = __builtin_bswap32(crc);
+    *reinterpret_cast<uint16_t*>(const_cast<uint8_t*>(&data[0x18])) = *reinterpret_cast<const uint16_t*>(GRAYSCALE_ALPHA);
+  }
+}
 
 void RosCompressedStreamer::imageCallback(const sensor_msgs::CompressedImageConstPtr &msg) {
   boost::mutex::scoped_lock lock(send_mutex_); // protects last_msg and last_frame