Continue work on png writer.

src/image/PngElements.h

@@ -1,5 +1,7 @@
 #pragma once
 
+#include "CyclicRedundancyChecker.h"
+
 #include <string>
 #include <sstream>
 
@@ -15,15 +17,23 @@ namespace Png
         return {13, 10, 26, 10};
     }
 
+    inline std::string getName()
+    {
+        return "PNG";
+    }
+
     struct IHDRChunk
     {
-        unsigned width{0};
-        unsigned height{0};
-        char bitDepth{0};
-        char colorType{0};
-        char compressionMethod{0};
-        char filterMethod{0};
-        char interlaceMethod{0};
+        uint32_t width{0};
+        uint32_t height{0};
+        unsigned char bitDepth{0};
+        unsigned char colorType{0};
+        unsigned char compressionMethod{0};
+        unsigned char filterMethod{0};
+        unsigned char interlaceMethod{0};
+        std::string name{"IHDR"};
+
+        std::vector<unsigned char> mData;
 
         std::string toString() const
         {
@@ -37,6 +47,42 @@ namespace Png
             sstr << "interlaceMethod: " << (int)interlaceMethod << "\n";
             return sstr.str();
         }
+
+        uint32_t getLength() const
+        {
+            return 13;
+        }
+
+        void updateData()
+        {
+            mData.clear();
+            unsigned num_bytes = sizeof(uint32_t);
+
+            for(unsigned idx=0; idx<num_bytes;idx++)
+            {
+                mData.push_back(ByteUtils::getByteN(width, idx));
+            }
+
+            for(unsigned idx=0; idx<num_bytes;idx++)
+            {
+                mData.push_back(ByteUtils::getByteN(height, idx));
+            }
+            mData.push_back(bitDepth);
+            mData.push_back(colorType);
+            mData.push_back(compressionMethod);
+            mData.push_back(filterMethod);
+            mData.push_back(interlaceMethod);
+        }
+
+        uint32_t getCrc() const
+        {
+            CyclicRedundancyChecker crc_check;
+            std::vector<unsigned char> char_data = StringUtils::toBytes(name);
+            std::copy(mData.begin(), mData.end(), std::back_inserter(char_data));
+
+            auto result = crc_check.doCrc(char_data.data(), char_data.size());
+            return result;
+        }
     };
 }