3 files changed, 34 insertions, 0 deletions
diff --git a/indra/llkdu/llimagej2ckdu.cpp b/indra/llkdu/llimagej2ckdu.cpp
index e7ac6bdb31..4330b1e5b1 100644
--- a/indra/llkdu/llimagej2ckdu.cpp
+++ b/indra/llkdu/llimagej2ckdu.cpp
@@ -1513,3 +1513,33 @@ void kdc_flow_control::process_components()
         }
     }
 }
+
+// Layer-factored byte estimator. Walks the resolution pyramid to count
+// layers, weights by layer_factor, then picks between a sqrt-based "new"
+// estimate and a raw-dimensions "old" estimate per TextureNewByteRange.
+// Reference: https://wiki.lindenlab.com/wiki/THX1138_KDU_Improvements#Byte_Range_Study
+S32 LLImageJ2CKDU::estimateDataSize(S32 w, S32 h, S32 comp, S32 discard_level, F32 rate) const
+{
+    S32 width  = (w > 0) ? w : 2048;
+    S32 height = (h > 0) ? h : 2048;
+    S32 nb_layers = 1;
+    S32 surface = width * height;
+    S32 s = MAX_BLOCK_SIZE * MAX_BLOCK_SIZE;
+    while (surface > s)
+    {
+        nb_layers++;
+        s *= 4;
+    }
+    F32 layer_factor = 3.0f * (7 - llclamp(nb_layers, 1, 6));
+
+    width  >>= discard_level;
+    height >>= discard_level;
+    width  = llmax(width, 1);
+    height = llmax(height, 1);
+
+    S32 new_bytes = (S32)(sqrtf((F32)(width * height)) * (F32)comp * rate * 1000.f / layer_factor);
+    S32 old_bytes = (S32)((F32)(width * height * comp) * rate);
+    S32 bytes = (LLImage::useNewByteRange() && (new_bytes < old_bytes)) ? new_bytes : old_bytes;
+    bytes = llmax(bytes, LLImageJ2C::calcHeaderSizeJ2C());
+    return bytes;
+}
diff --git a/indra/llkdu/llimagej2ckdu.h b/indra/llkdu/llimagej2ckdu.h
index c9aa0c5250..6079585948 100644
--- a/indra/llkdu/llimagej2ckdu.h
+++ b/indra/llkdu/llimagej2ckdu.h
@@ -67,6 +67,8 @@ protected:
     virtual bool initDecode(LLImageJ2C &base, LLImageRaw &raw_image, int discard_level = -1, int* region = NULL);
     virtual bool initEncode(LLImageJ2C &base, LLImageRaw &raw_image, int blocks_size = -1, int precincts_size = -1, int levels = 0);
     virtual std::string getEngineInfo() const;
+public:
+    virtual S32 estimateDataSize(S32 w, S32 h, S32 comp, S32 discard_level, F32 rate) const;
 
 private:
     bool initDecode(LLImageJ2C &base, LLImageRaw &raw_image, F32 decode_time, ECodeStreamMode mode, S32 first_channel, S32 max_channel_count, int discard_level = -1, int* region = NULL);
diff --git a/indra/llkdu/tests/llimagej2ckdu_test.cpp b/indra/llkdu/tests/llimagej2ckdu_test.cpp
index bc52a15c4a..6be2d3a078 100644
--- a/indra/llkdu/tests/llimagej2ckdu_test.cpp
+++ b/indra/llkdu/tests/llimagej2ckdu_test.cpp
@@ -83,6 +83,8 @@ void LLImageBase::setSize(S32 , S32 , S32 ) { }
 bool LLImageBase::isBufferInvalid() const { return false; }
 
 LLImageJ2CImpl::~LLImageJ2CImpl() { }
+bool LLImage::sUseNewByteRange = false;
+S32 LLImageJ2C::calcHeaderSizeJ2C() { return 0; }
 
 LLImageFormatted::LLImageFormatted(S8 ) { }
 LLImageFormatted::~LLImageFormatted() { }