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include/avif/internal.h

@@ -197,6 +197,7 @@ typedef struct avifSampleTransformToken
 {
     uint8_t type;                // avifSampleTransformTokenType
     int32_t constant;            // If value is AVIF_SAMPLE_TRANSFORM_CONSTANT.
+                                 // Only 32-bit (bit_depth=2) constants are supported.
     uint8_t inputImageItemIndex; // If value is AVIF_SAMPLE_TRANSFORM_INPUT_IMAGE_ITEM_INDEX. 1-based.
 } avifSampleTransformToken;
 

src/read.c

@@ -2024,6 +2024,7 @@ static avifBool avifParseToneMappedImageBox(avifGainMapMetadata * metadata, cons
 #endif // AVIF_ENABLE_EXPERIMENTAL_GAIN_MAP
 
 #if defined(AVIF_ENABLE_EXPERIMENTAL_SAMPLE_TRANSFORM)
+// bit-depth is assumed to be 2 (32-bit).
 static avifResult avifParseSampleTransformTokens(avifROStream * s, avifSampleTransformExpression * expression)
 {
     uint8_t tokenCount;
@@ -2036,7 +2037,7 @@ static avifResult avifParseSampleTransformTokens(avifROStream * s, avifSampleTra
 
         AVIF_CHECK(avifROStreamRead(s, &token->type, /*size=*/1)); // unsigned int(8) token;
         if (token->type == AVIF_SAMPLE_TRANSFORM_CONSTANT) {
-            // TODO(yguyon): Verify two's complement representation is guaranteed here.
+            // Two's complement representation is assumed here.
             uint32_t constant;
             AVIF_CHECK(avifROStreamReadU32(s, &constant)); // signed int(1<<(bit_depth+3)) constant;
             token->constant = *(int32_t *)&constant;       // maybe =(int32_t)constant; is enough
@@ -2166,11 +2167,11 @@ static avifResult avifDecoderItemReadAndParse(const avifDecoder * decoder,
         *codecType = avifGetCodecType(item->type);
         AVIF_ASSERT_OR_RETURN(*codecType != AVIF_CODEC_TYPE_UNKNOWN);
     }
-    // Note: If AVIF_ENABLE_EXPERIMENTAL_SAMPLE_TRANSFORM is defined, backward-incompatible files
-    //       with a primary 'sato' Sample Transform derived image item could be handled here
-    //       (compared to backward-compatible files with a 'sato' item in the same 'altr' group
-    //       as the primary regular color item which are handled in
-    //       avifDecoderDataFindSampleTransformImageItem() below).
+    // TODO(yguyon): If AVIF_ENABLE_EXPERIMENTAL_SAMPLE_TRANSFORM is defined, backward-incompatible
+    //               files with a primary 'sato' Sample Transform derived image item could be
+    //               handled here (compared to backward-compatible files with a 'sato' item in the
+    //               same 'altr' group as the primary regular color item which are handled in
+    //               avifDecoderDataFindSampleTransformImageItem() below).
     return AVIF_RESULT_OK;
 }
 
@@ -5155,6 +5156,8 @@ avifResult avifDecoderReset(avifDecoder * decoder)
                 // Input image item order is important because input image items are indexed according to this order.
                 AVIF_CHECKERR(inputImageItem->dimgIdx == data->sampleTransformNumInputImageItems, AVIF_RESULT_NOT_IMPLEMENTED);
 
+                AVIF_CHECKERR(data->sampleTransformNumInputImageItems < AVIF_SAMPLE_TRANSFORM_MAX_NUM_INPUT_IMAGE_ITEMS,
+                              AVIF_RESULT_NOT_IMPLEMENTED);
                 avifItemCategory * category = &data->sampleTransformInputImageItems[data->sampleTransformNumInputImageItems];
                 avifBool foundItem = AVIF_FALSE;
                 uint32_t alphaCategory = AVIF_ITEM_CATEGORY_COUNT;
@@ -5646,6 +5649,7 @@ avifResult avifDecoderApplySampleTransform(const avifDecoder * decoder, avifImag
     }
 
     for (avifBool alpha = AVIF_FALSE; alpha <= decoder->alphaPresent ? AVIF_TRUE : AVIF_FALSE; ++alpha) {
+        AVIF_ASSERT_OR_RETURN(decoder->data->sampleTransformNumInputImageItems <= AVIF_SAMPLE_TRANSFORM_MAX_NUM_INPUT_IMAGE_ITEMS);
         const avifImage * inputImages[AVIF_SAMPLE_TRANSFORM_MAX_NUM_INPUT_IMAGE_ITEMS];
         for (uint32_t i = 0; i < decoder->data->sampleTransformNumInputImageItems; ++i) {
             avifItemCategory category = decoder->data->sampleTransformInputImageItems[i];

src/write.c

@@ -1161,6 +1161,24 @@ static const char infeNameGainMap[] = "GMap";
 static const char infeNameSampleTransform[] = "SampleTransform";
 #endif
 
+static const char * getInfeName(avifItemCategory itemCategory)
+{
+    if (avifIsAlpha(itemCategory)) {
+        return infeNameAlpha;
+    }
+#if defined(AVIF_ENABLE_EXPERIMENTAL_GAIN_MAP)
+    if (itemCategory == AVIF_ITEM_GAIN_MAP) {
+        return infeNameGainMap;
+    }
+#endif
+#if defined(AVIF_ENABLE_EXPERIMENTAL_SAMPLE_TRANSFORM)
+    if (itemCategory >= AVIF_SAMPLE_TRANSFORM_MIN_CATEGORY && itemCategory <= AVIF_SAMPLE_TRANSFORM_MAX_CATEGORY) {
+        return infeNameSampleTransform;
+    }
+#endif
+    return infeNameColor;
+}
+
 // Adds the items for a single cell or a grid of cells. Outputs the topLevelItemID which is
 // the only item if there is exactly one cell, or the grid item for multiple cells.
 // Note: The topLevelItemID output argument has the type uint16_t* instead of avifEncoderItem** because
@@ -1174,20 +1192,7 @@ static avifResult avifEncoderAddImageItems(avifEncoder * encoder,
                                            uint16_t * topLevelItemID)
 {
     const uint32_t cellCount = gridCols * gridRows;
-    const char * infeName;
-    if (avifIsAlpha(itemCategory)) {
-        infeName = infeNameAlpha;
-#if defined(AVIF_ENABLE_EXPERIMENTAL_GAIN_MAP)
-    } else if (itemCategory == AVIF_ITEM_GAIN_MAP) {
-        infeName = infeNameGainMap;
-#endif
-#if defined(AVIF_ENABLE_EXPERIMENTAL_SAMPLE_TRANSFORM)
-    } else if (itemCategory >= AVIF_SAMPLE_TRANSFORM_MIN_CATEGORY && itemCategory <= AVIF_SAMPLE_TRANSFORM_MAX_CATEGORY) {
-        infeName = infeNameSampleTransform;
-#endif
-    } else {
-        infeName = infeNameColor;
-    }
+    const char * infeName = getInfeName(itemCategory);
     const size_t infeNameSize = strlen(infeName) + 1;
 
     if (cellCount > 1) {