1 files changed, 29 insertions, 0 deletions
diff --git a/indra/llimagej2coj/llimagej2coj.cpp b/indra/llimagej2coj/llimagej2coj.cpp
index 7cfadb889d..488c07e1c9 100644
--- a/indra/llimagej2coj/llimagej2coj.cpp
+++ b/indra/llimagej2coj/llimagej2coj.cpp
@@ -919,3 +919,32 @@ bool LLImageJ2COJ::getMetadata(LLImageJ2C &base)
     base.setSize(width, height, components);
     return true;
 }
+
+
+// OpenJPEG-tuned byte estimator. Conservative pyramid walk that accounts for
+// OJ's whole-code-block decode behavior (even with strict mode off). Larger
+// images get a per-resolution multiplier so the byte range lands inside the
+// last needed code-block boundary.
+S32 LLImageJ2COJ::estimateDataSize(S32 w, S32 h, S32 comp, S32 discard_level, F32 rate) const
+{
+    constexpr S32 precision = 8;
+    constexpr S32 max_components = 4;
+    S32 width  = (w > 0) ? w : 2048;
+    S32 height = (h > 0) ? h : 2048;
+    S32 max_dimension = llmax(width, height);
+    S32 block_area = MAX_BLOCK_SIZE * MAX_BLOCK_SIZE;
+    S32 max_layers = (S32)llmax(llround(log2f((float)max_dimension) - log2f((float)MAX_BLOCK_SIZE)), 4);
+    block_area *= llmax(max_layers, 1);
+    S32 totalbytes = (S32)(MIN_LAYER_SIZE * max_components * precision);
+    S32 block_layers = 0;
+    while (block_layers <= max_layers)
+    {
+        if (block_layers <= (5 - discard_level))
+            totalbytes += (S32)(block_area * max_components * precision * rate);
+        block_layers++;
+        block_area *= 4;
+    }
+    totalbytes /= 8;
+    totalbytes += LLImageJ2C::calcHeaderSizeJ2C();
+    return totalbytes;
+}