From 41a6a0af084110b6e777ba97c5988ed46e793192 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=A9r=C3=B4me=20Martinez?= <jerome@mediaarea.net>
Date: Mon, 8 Oct 2018 10:24:59 +0200
Subject: [PATCH] Add CFA (Bayer) support

---
 ffv1.md | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/ffv1.md b/ffv1.md
index 7918e7c..454f11a 100644
--- a/ffv1.md
+++ b/ffv1.md
@@ -391,6 +391,10 @@ In JPEG2000-RCT, the coding order would be left to right and then top to bottom,
 
 Y[1,1] Y[2,1] Cb[1,1] Cb[2,1] Cr[1,1] Cr[2,1] Y[1,2] Y[2,2] Cb[1,2] Cb[2,2] Cr[1,2] Cr[2,2]
 
+### Color Filter Array
+
+(TODO)
+
 ## Coding of the Sample Difference
 
 Instead of coding the n+1 bits of the Sample Difference with Huffman or Range coding (or n+2 bits, in the case of RCT), only the n (or n+1) least significant bits are used, since this is sufficient to recover the original sample. In the equation below, the term "bits" represents bits_per_raw_sample+1 for RCT or bits_per_raw_sample otherwise:
@@ -714,6 +718,10 @@ Parameters( ) {                                               |
         for (i = 1; i < 256; i++)                             |
             state_transition_delta[ i ]                       | sr
     colorspace_type                                           | ur
+    if (colorspace_type == 2) {                               |
+        for( i = 0; i < 4; i++ ) {                            |
+            cfa_pattern [ i ]                                 | ur
+    }                                                         |
     if (version >= 1)                                         |
         bits_per_raw_sample                                   | ur
     chroma_planes                                             | br
@@ -808,10 +816,26 @@ If state_transition_delta is not present in the FFV1 bitstream, all Range coder
 |-------|:--------------------------------|:--------------------------------|:--------------------------------|
 | 0     | YCbCr                           | No Pixel transformation         | plane then line                 |
 | 1     | RGB                             | JPEG2000-RCT                    | line then plane                 |
+| 2     | Color Filter Array              | JPEG2000-RCT + G difference     | line then plane                 |
 | Other | reserved for future use         | reserved for future use         | reserved for future use         |
 
 Restrictions:  
 If `colorspace_type` is 1, then `chroma_planes` MUST be 1, `log2_h_chroma_subsample` MUST be 0, and `log2_v_chroma_subsample` MUST be 0.  
+If `colorspace_type` is 2, then `chroma_planes` MUST be 1, `log2_h_chroma_subsample` MUST be 0, and `log2_v_chroma_subsample` MUST be 0, transparency MUST be 1.  
+
+### cfa_pattern
+
+`cfa_pattern` indicates the actual color filter array geometric pattern of the image sensor used to capture the single sensor color image.  
+The pattern is provided per line top to bottom, and for each line left to right.  
+
+|value  | color                           |
+|-------|:--------------------------------|
+|0      |   red                           |
+|1      |   green                         |
+|2      |   blue                          |
+
+Restrictions:  
+At least 1 component of each color must be present.  
 
 ### chroma_planes