Fix T99565: Cycles reading TGA files with alpha different than Blender

Thanks to Lukas for tracking down the cause in OIIO.

1 files changed, 11 insertions, 2 deletions

diff --git a/intern/cycles/scene/image_oiio.cpp b/intern/cycles/scene/image_oiio.cpp
index 8792393e5a1..d59359970c6 100644
--- a/intern/cycles/scene/image_oiio.cpp
+++ b/intern/cycles/scene/image_oiio.cpp
@@ -192,8 +192,17 @@ bool OIIOImageLoader::load_pixels(const ImageMetaData &metadata,
     return false;
   }
 
-  const bool do_associate_alpha = associate_alpha &&
-                                  spec.get_int_attribute("oiio:UnassociatedAlpha", 0);
+  bool do_associate_alpha = false;
+  if (associate_alpha) {
+    do_associate_alpha = spec.get_int_attribute("oiio:UnassociatedAlpha", 0);
+
+    /* Workaround OIIO not detecting TGA file alpha the same as Blender (since #3019).
+     * We want anything not marked as premultiplied alpha to get associated. */
+    if (!do_associate_alpha && spec.alpha_channel != -1 &&
+        strcmp(in->format_name(), "targa") == 0) {
+      do_associate_alpha = spec.get_int_attribute("targa:alpha_type", -1) != 4;
+    }
+  }
 
   switch (metadata.type) {
     case IMAGE_DATA_TYPE_BYTE: