Changes to make SkPDiff more robost.

tools/skpdiff/SkPMetric.cpp

Index: tools/skpdiff/SkPMetric.cpp
diff --git a/tools/skpdiff/SkPMetric.cpp b/tools/skpdiff/SkPMetric.cpp
index 5b770b08bdbdee7e5803eb36a9dd317d4d69b6c9..0ca8ee1ec33d01ec0ed7fc007182ba533352a578 100644
--- a/tools/skpdiff/SkPMetric.cpp
+++ b/tools/skpdiff/SkPMetric.cpp
@@ -123,8 +123,14 @@ static void adobergb_to_cielab(float r, float g, float b, LAB* lab) {
 }
 
 /// Converts a 8888 bitmap to LAB color space and puts it into the output
-static void bitmap_to_cielab(const SkBitmap* bitmap, ImageLAB* outImageLAB) {
-    SkASSERT(bitmap->config() == SkBitmap::kARGB_8888_Config);
+static bool bitmap_to_cielab(const SkBitmap* bitmap, ImageLAB* outImageLAB) {
+    SkBitmap bm8888;
+    if (bitmap->config() != SkBitmap::kARGB_8888_Config) {
+        if (!bitmap->copyTo(&bm8888, SkBitmap::kARGB_8888_Config)) {
+            return false;
+        }
+        bitmap = &bm8888;
+    }
 
     int width = bitmap->width();
     int height = bitmap->height();
@@ -146,6 +152,7 @@ static void bitmap_to_cielab(const SkBitmap* bitmap, ImageLAB* outImageLAB) {
         }
     }
     bitmap->unlockPixels();
+    return true;
 }
 
 // From Barten SPIE 1989
@@ -269,6 +276,12 @@ static double pmetric(const ImageLAB* baselineLAB, const ImageLAB* testLAB, SkTD
         maxLevels++;
     }
 
+    // We'll be creating new arrays with maxLevels - 2, and ImageL3D requires maxLevels > 0,
+    // so just return failure if we're less than 3.
+    if (maxLevels <= 2) {
+        return 0.0;
+    }
+
     const float fov = SK_ScalarPI / 180.0f * 45.0f;
     float contrastSensitivityMax = contrast_sensitivity(3.248f, 100.0f);
     float pixelsPerDegree = width / (2.0f * tanf(fov * 0.5f) * 180.0f / SK_ScalarPI);
@@ -450,8 +463,9 @@ int SkPMetric::queueDiff(SkBitmap* baseline, SkBitmap* test) {
     ImageLAB baselineLAB(baseline->width(), baseline->height());
     ImageLAB testLAB(baseline->width(), baseline->height());
 
-    bitmap_to_cielab(baseline, &baselineLAB);
-    bitmap_to_cielab(test, &testLAB);
+    if (!bitmap_to_cielab(baseline, &baselineLAB) || !bitmap_to_cielab(test, &testLAB)) {
+        return diffID;
+    }
 
     diff.result = pmetric(&baselineLAB, &testLAB, &diff.poi);