add colortable support to imagegenerator

src/images/SkImageGenerator.cpp

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkImageGenerator.h"
+
+#ifndef SK_SUPPORT_LEGACY_IMAGEGENERATORAPI
+bool SkImageGenerator::getInfo(SkImageInfo* info) {
+    SkImageInfo dummy;
+    if (NULL == info) {
+        info = &dummy;
+    }
+    return this->onGetInfo(info);
+}
+
+bool SkImageGenerator::getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
+                                 SkPMColor ctable[], int* ctableCount) {
+    if (kIndex_8_SkColorType == info.colorType()) {
+        SkASSERT(ctable);
+        SkASSERT(ctableCount);
+    } else {
+        SkASSERT(NULL == ctable);
+        SkASSERT(NULL == ctableCount);
+    }
+
+    if (kUnknown_SkColorType == info.colorType()) {
+        return false;
+    }
+    if (NULL == pixels) {
+        return false;
+    }
+    if (rowBytes < info.minRowBytes()) {
+        return false;
+    }
+
+    bool success = this->onGetPixels(info, pixels, rowBytes, ctable, ctableCount);
+
+    if (success && (kIndex_8_SkColorType == info.colorType())) {
+        SkASSERT(*ctableCount >= 0 && *ctableCount <= 256);
+    }
+    return success;
+}
+
+bool SkImageGenerator::getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes) {
+    SkASSERT(kIndex_8_SkColorType != info.colorType());
+    if (kIndex_8_SkColorType == info.colorType()) {

[scroggo, 2014/05/27 18:31:23]

It seems like we typically do not recover after a failed assert. Is there a
reason this case is different? (Or are we just inconsistent/am I wrong?)

[reed1, 2014/05/27 18:47:34]

I am of (at least) two minds here:

1. SkASSERT is debug-only, so release builds would not catch this
2. Perhaps this can silently just return false

As written, this is implementing both ideas, which isn't strictly wrong, but is
odd. Do you have a preference?

[scroggo, 2014/05/27 19:08:06]

I think that's ok. If it ends up being a problem we can figure out why in debug.
In that case I'm not sure how someone is supposed to discover they made a
mistake.
I think it's fine as is. I just thought our general idealogy was to skip the
conditional branch in release and just use an assert in debug to catch an error.

+        return false;
+    }
+    return this->getPixels(info, pixels, rowBytes, NULL, NULL);
+}
+#endif
+
+/////////////////////////////////////////////////////////////////////////////////////////////
+
+SkData* SkImageGenerator::onRefEncodedData() {
+    return NULL;
+}
+
+bool SkImageGenerator::onGetInfo(SkImageInfo*) {
+    return false;
+}
+
+bool SkImageGenerator::onGetPixels(const SkImageInfo&, void*, size_t, SkPMColor*, int*) {
+    return false;
+}