Add a gdb viewer for skbitmap.

Change-Id: I0d021e5006c3424d1fcb5498385c192d569f2c42
Reviewed-on: https://skia-review.googlesource.com/61860
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Herb Derby <herb@google.com>

tools/gdb/bitmap.py

@@ -0,0 +1,83 @@
+# Copyright 2017 Google Inc.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""
+Visualize bitmaps in gdb.
+
+(gdb) source <path to this file>
+(gdb) sk_bitmap <symbol>
+
+This should pop up a window with the bitmap displayed.
+Right clicking should bring up a menu, allowing the
+bitmap to be saved to a file.
+"""
+
+import gdb
+from enum import Enum
+try:
+  from PIL import Image
+except ImportError:
+  import Image
+
+class ColorType(Enum):
+    unknown = 0
+    alpha_8 = 1
+    rgb_565 = 2
+    argb_4444 = 3
+    rgba_8888 = 4
+    bgra_8888 = 5
+    gray_8 = 6
+    rgba_F16 = 7
+
+class AlphaType(Enum):
+    unknown = 0
+    opaque = 1
+    premul = 2
+    unpremul = 3
+
+class sk_bitmap(gdb.Command):
+  """Displays the content of an SkBitmap image."""
+
+  def __init__(self):
+      super(sk_bitmap, self).__init__('sk_bitmap',
+                                      gdb.COMMAND_SUPPORT,
+                                      gdb.COMPLETE_FILENAME)
+
+  def invoke(self, arg, from_tty):
+    frame = gdb.selected_frame()
+    val = frame.read_var(arg)
+    if str(val.type.strip_typedefs()) == 'SkBitmap':
+      pixels = val['fPixels']
+      row_bytes = val['fRowBytes']
+      info = val['fInfo']
+      width = info['fWidth']
+      height = info['fHeight']
+      color_type = info['fColorType']
+      alpha_type = info['fAlphaType']
+
+      process = gdb.selected_inferior()
+      memory_data = process.read_memory(pixels, row_bytes * height)
+      size = (width, height)
+      image = None
+      # See Unpack.c for the values understood after the "raw" parameter.
+      if color_type == ColorType.bgra_8888.value:
+        if alpha_type == AlphaType.unpremul.value:
+          image = Image.frombytes("RGBA", size, memory_data.tobytes(),
+                                  "raw", "BGRA", row_bytes, 1)
+        elif alpha_type == AlphaType.premul.value:
+          # RGBA instead of RGBa, because Image.show() doesn't work with RGBa.
+          image = Image.frombytes("RGBA", size, memory_data.tobytes(),
+                                  "raw", "BGRa", row_bytes, 1)
+
+      if image:
+        # Fails on premultiplied alpha, it cannot convert to RGB.
+        image.show()
+      else:
+        print ("Need to add support for %s %s." % (
+               str(ColorType(int(color_type))),
+               str(AlphaType(int(alpha_type)))
+        ))
+
+sk_bitmap()