From d906731fa75b912e0be83603e5de336fbec6d2a4 Mon Sep 17 00:00:00 2001
From: mattmcw <matt@sixteenmillimeter.com>
Date: Thu, 7 Nov 2024 18:16:24 -0500
Subject: [PATCH] Updates to the DPX class to figure out header packing. Not
 working yet.

---
 src/dpx.cpp | 104 +++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 70 insertions(+), 34 deletions(-)

diff --git a/src/dpx.cpp b/src/dpx.cpp
index 58ba324..e8a7318 100644
--- a/src/dpx.cpp
+++ b/src/dpx.cpp
@@ -15,61 +15,97 @@ uint16_t DPX::swapEndian(uint16_t value) {
 }
 
 bool DPX::readHeader(ifstream& file) {
-    // Read magic number
+    // DPX Header Map for reference:
+    // 0x0000-0x0003: Magic number
+    // 0x0004-0x0007: Image data offset
+    // 0x0008-0x000B: Version number of header format
+    // 0x000C-0x000F: Total image file size
+    // 0x0010-0x0013: Ditto Key
+    // 0x0014-0x0017: Generic section header length
+    // 0x0018-0x001B: Industry specific header length
+    // 0x001C-0x001F: User defined header length
+    
+    // Read and check magic number
     file.read(reinterpret_cast<char*>(&header.magic), sizeof(header.magic));
     
-    // Check for both possible magic numbers (big and little endian)
-    const uint32_t MAGIC_BE = 0x53445058;  // "SDPX" in big endian
-    const uint32_t MAGIC_LE = 0x58504453;  // "XPDS" in little endian
+    const uint32_t MAGIC_BE = 0x53445058;  // "SDPX"
+    const uint32_t MAGIC_LE = 0x58504453;  // "XPDS"
     
-    cout << "{ \"dpx_magic_number\" : \"" << hex << header.magic << "\" }" << endl;
+    cout << "{ \"dpx_magic_number\" : \"0x" << hex << header.magic << dec << "\" }" << endl;
     
     if (header.magic == MAGIC_BE) {
         header.isBigEndian = true;
     } else if (header.magic == MAGIC_LE) {
         header.isBigEndian = false;
     } else {
-        uint32_t swapped_magic = swapEndian(header.magic);
-        cout << "{ \"dpx_swapped_magic_number\" : \"0x" << hex << swapped_magic << "\" }" << endl;
-        
-        if (swapped_magic == MAGIC_BE) {
-            header.isBigEndian = true;
-            header.magic = swapped_magic;
-        } else if (swapped_magic == MAGIC_LE) {
-            header.isBigEndian = false;
-            header.magic = swapped_magic;
-        } else {
-            throw runtime_error("Not a valid DPX file - Invalid magic number");
-        }
+        throw runtime_error("Not a valid DPX file - Invalid magic number");
     }
 
-    // Read image data offset
-    file.seekg(4);
-    file.read(reinterpret_cast<char*>(&header.imageOffset), sizeof(header.imageOffset));
-    if (header.isBigEndian) {
-        header.imageOffset = swapEndian(header.imageOffset);
+    // Read Core Header
+    uint32_t genericHeaderLength;
+    file.seekg(0x14);  // Go to generic header length
+    file.read(reinterpret_cast<char*>(&genericHeaderLength), sizeof(genericHeaderLength));
+    if (!header.isBigEndian) {
+        genericHeaderLength = swapEndian(genericHeaderLength);
     }
+    cout << "{ \"dpx_header_length\" : " << genericHeaderLength << " }" << endl;
 
-    // Seek to image information offset (768 bytes from start)
-    file.seekg(768);
+    // Image Information Header starts at 0x0200 (512)
+    file.seekg(0x0200);
+    
+    // Read orientation
+    uint32_t orientation;
+    file.read(reinterpret_cast<char*>(&orientation), sizeof(orientation));
+    if (!header.isBigEndian) {
+        orientation = swapEndian(orientation);
+    }
+    
+    // Read number of image elements
+    uint16_t numberOfElements;
+    file.read(reinterpret_cast<char*>(&numberOfElements), sizeof(numberOfElements));
+    if (!header.isBigEndian) {
+        numberOfElements = swapEndian(numberOfElements);
+    }
+    
+    // Read image dimensions
     file.read(reinterpret_cast<char*>(&header.width), sizeof(header.width));
     file.read(reinterpret_cast<char*>(&header.height), sizeof(header.height));
-    
-    if (header.isBigEndian) {
+    if (!header.isBigEndian) {
         header.width = swapEndian(header.width);
         header.height = swapEndian(header.height);
     }
+    
+    cout << "{ \"dpx_width\" : " << header.width << ", \"dpx_height\" :" << header.height << " }" << endl;
 
-    cout << "{ \"dimensions\" : { \"width\" : " << header.width << ", \"height\" :" << header.height << " }, ";
-
-    // Read image element information (1556 bytes from start)
-    file.seekg(1556);
-    file.read(reinterpret_cast<char*>(&header.descriptor), sizeof(header.descriptor));
+    // Image Element Information starts at 0x0604 (1540)
+    file.seekg(0x0604);
+    
+    // Read data sign (0 = unsigned)
+    uint32_t dataSign;
+    file.read(reinterpret_cast<char*>(&dataSign), sizeof(dataSign));
+    if (!header.isBigEndian) {
+        dataSign = swapEndian(dataSign);
+    }
+    
+    // Read bit depth
     file.read(reinterpret_cast<char*>(&header.bitDepth), sizeof(header.bitDepth));
-    file.read(reinterpret_cast<char*>(&header.imageElements), sizeof(header.imageElements));
+    cout << "{ \"dpx_bit_depth\" : " << static_cast<int>(header.bitDepth) << " }"<< endl;
+    
+    // Read packing method
+    uint16_t packing;
+    file.read(reinterpret_cast<char*>(&packing), sizeof(packing));
+    if (!header.isBigEndian) {
+        packing = swapEndian(packing);
+    }
+    cout << "{ \"dpx_packing\" : " << packing << " }" << endl;
 
-    cout << " \"bit_depth\" : " << static_cast<int>(header.bitDepth) << ", ";
-    cout << " \"offset\": " << header.imageOffset << " }" << endl;
+    // Read image offset (from start of file)
+    file.seekg(0x04);
+    file.read(reinterpret_cast<char*>(&header.imageOffset), sizeof(header.imageOffset));
+    if (!header.isBigEndian) {
+        header.imageOffset = swapEndian(header.imageOffset);
+    }
+    cout << "{ \"dpx_offset\" : " << header.imageOffset << " }" << endl;
 
     return true;
 }