* Additional changes for PR #477

* clang-format all files
* Make it clear in avifenc syntax that -p signals prem in the resultant AVIF
* Fix tref prem parsing to match tref auxl parsing (same syntax/box)
* parenthesize binops in assignments (style)
* Continue new convertResult pattern in avifImageYUVToRGB instead of early-out
* Replace pColorIrefType/pColorIrefToID with new avifEncoderDataFindItemByID() call, as
  avifEncoderItem* mem storage may shift during new calls to avifEncoderDataCreateItem() so
  deep pointers into them during this is bad, plus this happens to remove accidental
  Hungarian notation, which is good

src/alpha.c

diff --git a/src/alpha.c b/src/alpha.c
index fa1d551..e3301ae 100644
--- a/src/alpha.c
+++ b/src/alpha.c
@@ -3,8 +3,8 @@
 
 #include "avif/internal.h"
 
-#include <string.h>
 #include <assert.h>
+#include <string.h>
 
 static int calcMaxChannel(uint32_t depth, avifRange range)
 {
@@ -382,7 +382,8 @@
     return AVIF_TRUE;
 }
 
-avifResult avifRGBImagePremultiplyAlpha(avifRGBImage * rgb) {
+avifResult avifRGBImagePremultiplyAlpha(avifRGBImage * rgb)
+{
     // no data
     if (!rgb->pixels || !rgb->rowBytes) {
         return AVIF_RESULT_REFORMAT_FAILED;

src/read.c

diff --git a/src/read.c b/src/read.c
index 941b20d..db18c9a 100644
--- a/src/read.c
+++ b/src/read.c
@@ -2033,12 +2033,13 @@
 
         if (!memcmp(header.type, "auxl", 4)) {
             uint32_t toID;
-            CHECK(avifROStreamReadU32(&s, &toID));                       // unsigned int(32) track_IDs[]
+            CHECK(avifROStreamReadU32(&s, &toID));                       // unsigned int(32) track_IDs[];
             CHECK(avifROStreamSkip(&s, header.size - sizeof(uint32_t))); // just take the first one
             track->auxForID = toID;
         } else if (!memcmp(header.type, "prem", 4)) {
             uint32_t byID;
-            CHECK(avifROStreamReadU32(&s, &byID));                       // unsigned int(32) to_item_ID
+            CHECK(avifROStreamReadU32(&s, &byID));                       // unsigned int(32) track_IDs[];
+            CHECK(avifROStreamSkip(&s, header.size - sizeof(uint32_t))); // just take the first one
             track->premByID = byID;
         } else {
             CHECK(avifROStreamSkip(&s, header.size));
@@ -2613,7 +2614,7 @@
         decoder->image->width = colorTrack->width;
         decoder->image->height = colorTrack->height;
         decoder->alphaPresent = (alphaTrack != NULL);
-        decoder->image->alphaPremultiplied = decoder->alphaPresent && colorTrack->premByID == alphaTrack->id;
+        decoder->image->alphaPremultiplied = decoder->alphaPresent && (colorTrack->premByID == alphaTrack->id);
     } else {
         // Create from items
 
@@ -2770,7 +2771,7 @@
             decoder->image->height = 0;
         }
         decoder->alphaPresent = (alphaItem != NULL);
-        decoder->image->alphaPremultiplied = decoder->alphaPresent && colorItem->premByID == alphaItem->id;
+        decoder->image->alphaPremultiplied = decoder->alphaPresent && (colorItem->premByID == alphaItem->id);
     }
 
     // Sanity check tiles

src/reformat.c

diff --git a/src/reformat.c b/src/reformat.c
index 047b8c1..54a3058 100644
--- a/src/reformat.c
+++ b/src/reformat.c
@@ -1138,9 +1138,9 @@
 
     if (avifRGBFormatHasAlpha(rgb->format) && !rgb->ignoreAlpha) {
         if (image->alphaPremultiplied && !rgb->alphaPremultiplied) {
-            return avifRGBImageUnpremultiplyAlpha(rgb);
+            convertResult = avifRGBImageUnpremultiplyAlpha(rgb);
         } else if (!image->alphaPremultiplied && rgb->alphaPremultiplied) {
-            return avifRGBImagePremultiplyAlpha(rgb);
+            convertResult = avifRGBImagePremultiplyAlpha(rgb);
         }
     }
 

src/write.c

diff --git a/src/write.c b/src/write.c
index e8ae8ac..b65f993 100644
--- a/src/write.c
+++ b/src/write.c
@@ -3,6 +3,7 @@
 
 #include "avif/internal.h"
 
+#include <assert.h>
 #include <string.h>
 #include <time.h>
 
@@ -145,6 +146,17 @@
     return item;
 }
 
+static avifEncoderItem * avifEncoderDataFindItemByID(avifEncoderData * data, uint16_t id)
+{
+    for (uint32_t itemIndex = 0; itemIndex < data->items.count; ++itemIndex) {
+        avifEncoderItem * item = &data->items.item[itemIndex];
+        if (item->id == id) {
+            return item;
+        }
+    }
+    return NULL;
+}
+
 static void avifEncoderDataDestroy(avifEncoderData * data)
 {
     for (uint32_t i = 0; i < data->items.count; ++i) {
@@ -461,9 +473,6 @@
 
         // Prepare all AV1 items
 
-        const char ** pColorIrefType = NULL;
-        uint16_t * pColorIrefToID = NULL;
-
         uint16_t gridColorID = 0;
         if (cellCount > 1) {
             avifEncoderItem * gridColorItem = avifEncoderDataCreateItem(encoder->data, "grid", "Color", 6, 0);
@@ -473,8 +482,6 @@
 
             gridColorID = gridColorItem->id;
             encoder->data->primaryItemID = gridColorID;
-            pColorIrefType = &gridColorItem->irefType;
-            pColorIrefToID = &gridColorItem->irefToID;
         }
 
         for (uint32_t cellIndex = 0; cellIndex < cellCount; ++cellIndex) {
@@ -490,8 +497,6 @@
                 item->dimgFromID = gridColorID;
             } else {
                 encoder->data->primaryItemID = item->id;
-                pColorIrefType = &item->irefType;
-                pColorIrefToID = &item->irefToID;
             }
         }
 
@@ -529,8 +534,10 @@
                 gridAlphaID = gridAlphaItem->id;
 
                 if (encoder->data->imageMetadata->alphaPremultiplied) {
-                    *pColorIrefType = "prem";
-                    *pColorIrefToID = gridAlphaID;
+                    avifEncoderItem * primaryItem = avifEncoderDataFindItemByID(encoder->data, encoder->data->primaryItemID);
+                    assert(primaryItem);
+                    primaryItem->irefType = "prem";
+                    primaryItem->irefToID = gridAlphaID;
                 }
             }
 
@@ -550,8 +557,10 @@
                     item->irefType = "auxl";
 
                     if (encoder->data->imageMetadata->alphaPremultiplied) {
-                        *pColorIrefType = "prem";
-                        *pColorIrefToID = item->id;
+                        avifEncoderItem * primaryItem = avifEncoderDataFindItemByID(encoder->data, encoder->data->primaryItemID);
+                        assert(primaryItem);
+                        primaryItem->irefType = "prem";
+                        primaryItem->irefToID = item->id;
                     }
                 }
             }