GIF decode: optional error messages and fault tolerance.

Add new runtime configuration variable,
images.gif.suppressDecoderWarnings, which suppresses warning and
errors from the GIF library.  It defaults to "true", which is current
behavior.

(This setting can be changed by setting the environment variable
skia_images_gif_suppressDecoderWarnings="false".)

Some conditions which were errors before are now warnings:

-   If the image width or height is greater than the GIF screen width or
    height (respectively) we expand the screen to hold the image.

-   If the offset of the image inside the screen would place the
    image outside of the screen, we shift the image to fix this.

-   If the image lacks a color table, we create a default color table.

-   If the image is truncated, then the rest of the image is filled with
    the fill color.

In all four cases, if images.gif.suppressDecoderWarnings is set to
false, then a warning message is printed via SkDebugf.

In the event of another kind of error, SkGIFImageDecoder::onDecode()
will still return false.  But with this change, if
images.gif.suppressDecoderWarnings is set to false, a description of
the error is printed via SkDebugf.

Also, added a new unit test GifTest, which tests the deconing of both
good GIf files and corrupted files that should now work with this
change.  This unit test is disabled on Win32, iOS, and Mac.

BUG=skia:1689
R=scroggo@google.com

Review URL: https://codereview.chromium.org/26743002

git-svn-id: http://skia.googlecode.com/svn/trunk@11734 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 210 insertions, 0 deletions

diff --git a/tests/GifTest.cpp b/tests/GifTest.cpp
new file mode 100644
index 0000000000..5919b44d68
--- /dev/null
+++ b/tests/GifTest.cpp
@@ -0,0 +1,210 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+// This tests out GIF decoder (SkImageDecoder_libgif.cpp)
+// It is not used on these platforms:
+#if (!defined(SK_BUILD_FOR_WIN32)) &&           \
+    (!defined(SK_BUILD_FOR_IOS)) &&             \
+    (!defined(SK_BUILD_FOR_MAC))
+
+#include "SkBitmap.h"
+#include "SkData.h"
+#include "SkForceLinking.h"
+#include "SkImageDecoder.h"
+#include "SkImage.h"
+#include "SkStream.h"
+#include "Test.h"
+
+__SK_FORCE_IMAGE_DECODER_LINKING;
+
+namespace {
+    unsigned char gifData[] = {
+        0x47, 0x49, 0x46, 0x38, 0x37, 0x61, 0x03, 0x00,
+        0x03, 0x00, 0xe3, 0x08, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0xff, 0xff, 0x00, 0x00, 0xff, 0x00,
+        0xff, 0x80, 0x80, 0x80, 0x00, 0xff, 0x00, 0x00,
+        0xff, 0xff, 0xff, 0xff, 0x00, 0xff, 0xff, 0xff,
+        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+        0xff, 0xff, 0xff, 0xff, 0xff, 0x2c, 0x00, 0x00,
+        0x00, 0x00, 0x03, 0x00, 0x03, 0x00, 0x00, 0x04,
+        0x07, 0x50, 0x1c, 0x43, 0x40, 0x41, 0x23, 0x44,
+        0x00, 0x3b};
+    unsigned char gifDataNoColormap[] = {
+        0x47, 0x49, 0x46, 0x38, 0x39, 0x61, 0x01, 0x00,
+        0x01, 0x00, 0x00, 0x00, 0x00, 0x21, 0xf9, 0x04,
+        0x01, 0x0a, 0x00, 0x01, 0x00, 0x2c, 0x00, 0x00,
+        0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x02,
+        0x02, 0x4c, 0x01, 0x00, 0x3b};
+    unsigned char interlacedGif[] = {
+        0x47, 0x49, 0x46, 0x38, 0x37, 0x61, 0x09, 0x00,
+        0x09, 0x00, 0xe3, 0x08, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0xff, 0xff, 0x00, 0x00, 0xff, 0x00,
+        0xff, 0x80, 0x80, 0x80, 0x00, 0xff, 0x00, 0x00,
+        0xff, 0xff, 0xff, 0xff, 0x00, 0xff, 0xff, 0xff,
+        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+        0xff, 0xff, 0xff, 0xff, 0xff, 0x2c, 0x00, 0x00,
+        0x00, 0x00, 0x09, 0x00, 0x09, 0x00, 0x40, 0x04,
+        0x1b, 0x50, 0x1c, 0x23, 0xe9, 0x44, 0x23, 0x60,
+        0x9d, 0x09, 0x28, 0x1e, 0xf8, 0x6d, 0x64, 0x56,
+        0x9d, 0x53, 0xa8, 0x7e, 0xa8, 0x65, 0x94, 0x5c,
+        0xb0, 0x8a, 0x45, 0x04, 0x00, 0x3b};
+};  // namespace
+
+static void test_gif_data_no_colormap(skiatest::Reporter* r,
+                                  void* data, size_t size) {
+    SkBitmap bm;
+    bool imageDecodeSuccess = SkImageDecoder::DecodeMemory(
+        data, size, &bm);
+    REPORTER_ASSERT(r, imageDecodeSuccess);
+    REPORTER_ASSERT(r, bm.width() == 1);
+    REPORTER_ASSERT(r, bm.height() == 1);
+    REPORTER_ASSERT(r, !(bm.empty()));
+    if (!(bm.empty())) {
+        REPORTER_ASSERT(r, bm.getColor(0, 0) == 0x00000000);
+    }
+}
+static void test_gif_data(skiatest::Reporter* r, void* data, size_t size) {
+    SkBitmap bm;
+    bool imageDecodeSuccess = SkImageDecoder::DecodeMemory(
+        data, size, &bm);
+    REPORTER_ASSERT(r, imageDecodeSuccess);
+    REPORTER_ASSERT(r, bm.width() == 3);
+    REPORTER_ASSERT(r, bm.height() == 3);
+    REPORTER_ASSERT(r, !(bm.empty()));
+    if (!(bm.empty())) {
+        REPORTER_ASSERT(r, bm.getColor(0, 0) == 0xffff0000);
+        REPORTER_ASSERT(r, bm.getColor(1, 0) == 0xffffff00);
+        REPORTER_ASSERT(r, bm.getColor(2, 0) == 0xff00ffff);
+        REPORTER_ASSERT(r, bm.getColor(0, 1) == 0xff808080);
+        REPORTER_ASSERT(r, bm.getColor(1, 1) == 0xff000000);
+        REPORTER_ASSERT(r, bm.getColor(2, 1) == 0xff00ff00);
+        REPORTER_ASSERT(r, bm.getColor(0, 2) == 0xffffffff);
+        REPORTER_ASSERT(r, bm.getColor(1, 2) == 0xffff00ff);
+        REPORTER_ASSERT(r, bm.getColor(2, 2) == 0xff0000ff);
+    }
+}
+static void test_interlaced_gif_data(skiatest::Reporter* r,
+                                     void* data,
+                                     size_t size) {
+    SkBitmap bm;
+    bool imageDecodeSuccess = SkImageDecoder::DecodeMemory(
+        data, size, &bm);
+    REPORTER_ASSERT(r, imageDecodeSuccess);
+    REPORTER_ASSERT(r, bm.width() == 9);
+    REPORTER_ASSERT(r, bm.height() == 9);
+    REPORTER_ASSERT(r, !(bm.empty()));
+    if (!(bm.empty())) {
+        REPORTER_ASSERT(r, bm.getColor(0, 0) == 0xffff0000);
+        REPORTER_ASSERT(r, bm.getColor(1, 0) == 0xffffff00);
+        REPORTER_ASSERT(r, bm.getColor(2, 0) == 0xff00ffff);
+
+        REPORTER_ASSERT(r, bm.getColor(0, 2) == 0xffffffff);
+        REPORTER_ASSERT(r, bm.getColor(1, 2) == 0xffff00ff);
+        REPORTER_ASSERT(r, bm.getColor(2, 2) == 0xff0000ff);
+
+        REPORTER_ASSERT(r, bm.getColor(0, 4) == 0xff808080);
+        REPORTER_ASSERT(r, bm.getColor(1, 4) == 0xff000000);
+        REPORTER_ASSERT(r, bm.getColor(2, 4) == 0xff00ff00);
+
+        REPORTER_ASSERT(r, bm.getColor(0, 6) == 0xffff0000);
+        REPORTER_ASSERT(r, bm.getColor(1, 6) == 0xffffff00);
+        REPORTER_ASSERT(r, bm.getColor(2, 6) == 0xff00ffff);
+
+        REPORTER_ASSERT(r, bm.getColor(0, 8) == 0xffffffff);
+        REPORTER_ASSERT(r, bm.getColor(1, 8) == 0xffff00ff);
+        REPORTER_ASSERT(r, bm.getColor(2, 8) == 0xff0000ff);
+    }
+}
+
+static void test_gif_data_short(skiatest::Reporter* r,
+                                void* data,
+                                size_t size) {
+    SkBitmap bm;
+    bool imageDecodeSuccess = SkImageDecoder::DecodeMemory(
+        data, size, &bm);
+    REPORTER_ASSERT(r, imageDecodeSuccess);
+    REPORTER_ASSERT(r, bm.width() == 3);
+    REPORTER_ASSERT(r, bm.height() == 3);
+    REPORTER_ASSERT(r, !(bm.empty()));
+    if (!(bm.empty())) {
+        REPORTER_ASSERT(r, bm.getColor(0, 0) == 0xffff0000);
+        REPORTER_ASSERT(r, bm.getColor(1, 0) == 0xffffff00);
+        REPORTER_ASSERT(r, bm.getColor(2, 0) == 0xff00ffff);
+        REPORTER_ASSERT(r, bm.getColor(0, 1) == 0xff808080);
+        REPORTER_ASSERT(r, bm.getColor(1, 1) == 0xff000000);
+        REPORTER_ASSERT(r, bm.getColor(2, 1) == 0xff00ff00);
+    }
+}
+
+/**
+  This test will test the ability of the SkImageDecoder to deal with
+  GIF files which have been mangled somehow.  We want to display as
+  much of the GIF as possible.
+*/
+static void TestGif(skiatest::Reporter* reporter) {
+    // test perfectly good images.
+    test_gif_data(reporter, static_cast<void *>(gifData), sizeof(gifData));
+    test_interlaced_gif_data(reporter, static_cast<void *>(interlacedGif),
+                          sizeof(interlacedGif));
+
+    unsigned char badData[sizeof(gifData)];
+
+    /* If you set the environment variable
+       skia_images_gif_suppressDecoderWarnings to 'false', you will
+       see warnings on stderr.  This is a feature.  */
+
+    memcpy(badData, gifData, sizeof(gifData));
+    badData[6] = 0x01;  // image too wide
+    test_gif_data(reporter, static_cast<void *>(badData), sizeof(gifData));
+    // "libgif warning [image too wide, expanding output to size]"
+
+    memcpy(badData, gifData, sizeof(gifData));
+    badData[8] = 0x01;  // image too tall
+    test_gif_data(reporter, static_cast<void *>(badData), sizeof(gifData));
+    // "libgif warning [image too tall,  expanding output to size]"
+
+    memcpy(badData, gifData, sizeof(gifData));
+    badData[62] = 0x01;  // image shifted right
+    test_gif_data(reporter, static_cast<void *>(badData), sizeof(gifData));
+    // "libgif warning [shifting image left to fit]"
+
+    memcpy(badData, gifData, sizeof(gifData));
+    badData[64] = 0x01;  // image shifted down
+    test_gif_data(reporter, static_cast<void *>(badData), sizeof(gifData));
+    // "libgif warning [shifting image up to fit]"
+
+    memcpy(badData, gifData, sizeof(gifData));
+    badData[62] = 0xff;  // image shifted left
+    badData[63] = 0xff;  // 2's complement -1 short
+    test_gif_data(reporter, static_cast<void *>(badData), sizeof(gifData));
+    // "libgif warning [shifting image left to fit]"
+
+    memcpy(badData, gifData, sizeof(gifData));
+    badData[64] = 0xff;  // image shifted up
+    badData[65] = 0xff;  // 2's complement -1 short
+    test_gif_data(reporter, static_cast<void *>(badData), sizeof(gifData));
+    // "libgif warning [shifting image up to fit]"
+
+    test_gif_data_no_colormap(reporter, static_cast<void *>(gifDataNoColormap),
+                              sizeof(gifDataNoColormap));
+    // "libgif warning [missing colormap]"
+
+    // test short Gif.  80 is missing a few bytes.
+    test_gif_data_short(reporter, static_cast<void *>(gifData), 80);
+    // "libgif warning [DGifGetLine]"
+
+    test_interlaced_gif_data(reporter, static_cast<void *>(interlacedGif),
+                             100);  // 100 is missing a few bytes
+    // "libgif warning [interlace DGifGetLine]"
+}
+
+#include "TestClassDef.h"
+DEFINE_TESTCLASS("GifTest", GifTestClass, TestGif)
+
+#endif  // !(SK_BUILD_FOR_WIN32||SK_BUILD_FOR_IOS||SK_BUILD_FOR_MAC)