Enabling ico decoding with use of png and bmp decoders

src/codec/SkCodec_libico.cpp

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkCodec_libbmp.h"
+#include "SkCodec_libico.h"
+#include "SkCodec_libpng.h"
+#include "SkCodecPriv.h"
+#include "SkColorPriv.h"
+#include "SkData.h"
+#include "SkStream.h"
+#include "SkTDArray.h"
+#include "SkTSort.h"
+
+/*
+ * Checks the start of the stream to see if the image is an Ico or Cur
+ */
+bool SkIcoCodec::IsIco(SkStream* stream) {
+    const char icoSig[] = { '\x00', '\x00', '\x01', '\x00' };
+    const char curSig[] = { '\x00', '\x00', '\x02', '\x00' };
+    char buffer[sizeof(icoSig)];
+    return stream->read(buffer, sizeof(icoSig)) == sizeof(icoSig) &&
+            (!memcmp(buffer, icoSig, sizeof(icoSig)) ||
+            !memcmp(buffer, curSig, sizeof(curSig)));
+}
+
+/*
+ * Assumes IsIco was called and returned true
+ * Creates an Ico decoder
+ * Reads enough of the stream to determine the image format
+ */
+SkCodec* SkIcoCodec::NewFromStream(SkStream* stream) {
+    // Header size constants
+    static const uint32_t kIcoDirectoryBytes = 6;
+    static const uint32_t kIcoDirEntryBytes = 16;
+
+    // Read the directory header
+    SkAutoTDeleteArray<uint8_t> dirBuffer(
+            SkNEW_ARRAY(uint8_t, kIcoDirectoryBytes));
+    if (stream->read(dirBuffer.get(), kIcoDirectoryBytes) !=
+            kIcoDirectoryBytes) {
+        SkDebugf("Error: unable to read ico directory header.\n");
+        return NULL;
+    }
+
+    // Process the directory header
+    const uint16_t numImages = get_short(dirBuffer.get(), 4);
+    if (0 == numImages) {
+        SkDebugf("Error: No images embedded in ico.\n");
+        return NULL;
+    }
+
+    // Ensure that we can read all of indicated directory entries
+    SkAutoTDeleteArray<uint8_t> entryBuffer(
+            SkNEW_ARRAY(uint8_t, numImages*kIcoDirEntryBytes));
+    if (stream->read(entryBuffer.get(), numImages*kIcoDirEntryBytes) !=
+            numImages*kIcoDirEntryBytes) {
+        SkDebugf("Error: unable to read ico directory entries.\n");
+        return NULL;
+    }
+
+    // This structure is used to represent the vital information about entries
+    // in the directory header.  We will obtain this information for each
+    // directory entry.
+    struct Entry {
+        uint32_t offset;
+        uint32_t size;
+    };
+    SkAutoTDeleteArray<Entry> directoryEntries(SkNEW_ARRAY(Entry, numImages));
+
+    // Iterate over directory entries
+    for (uint32_t i = 0; i < numImages; i++) {
+        // The directory entry contains information such as width, height,
+        // bits per pixel, and number of colors in the color palette.  We will
+        // ignore these fields since they are repeated in the header of the
+        // embedded image.  In the event of an inconsistency, we would always
+        // defer to the value in the embedded header anyway.
+
+        // Specifies the size of the embedded image, including the header
+        uint32_t size = get_int(entryBuffer.get(), 8 + i*kIcoDirEntryBytes);
+
+        // Specifies the offset of the embedded image from the start of file.
+        // It does not indicate the start of the pixel data, but rather the
+        // start of the embedded image header.
+        uint32_t offset = get_int(entryBuffer.get(), 12 + i*kIcoDirEntryBytes);
+
+        // Save the vital fields
+        directoryEntries.get()[i].offset = offset;
+        directoryEntries.get()[i].size = size;
+    }
+
+    // It is "customary" that the embedded images will be stored in order of
+    // increasing offset.  However, the specification does not indicate that
+    // they must be stored in this order, so we will not trust that this is the
+    // case.  Here we sort the embedded images by increasing offset.
+    struct EntryLessThan {
+        bool operator() (Entry a, Entry b) const {
+            return a.offset < b.offset;
+        }
+    };
+    EntryLessThan lessThan;
+    SkTQSort(directoryEntries.get(), directoryEntries.get() + numImages - 1,
+            lessThan);
+
+    // Now will construct a candidate codec for each of the embedded images
+    uint32_t bytesRead = kIcoDirectoryBytes + numImages * kIcoDirEntryBytes;
+    SkAutoTDelete<SkTArray<SkAutoTDelete<SkCodec>, true>> codecs(
+            SkNEW_ARGS((SkTArray<SkAutoTDelete<SkCodec>, true>), (numImages)));
+    for (uint32_t i = 0; i < numImages; i++) {
+        uint32_t offset = directoryEntries.get()[i].offset;
+        uint32_t size = directoryEntries.get()[i].size;
+        
+        // Ensure that the offset is valid
+        if (offset < bytesRead) {
+            SkDebugf("Warning: invalid ico offset.\n");
+            continue;
+        }
+
+        // If we cannot skip, assume we have reached the end of the stream and
+        // stop trying to make codecs
+        if (stream->skip(offset - bytesRead) != offset - bytesRead) {
+            SkDebugf("Warning: could not skip to ico offset.\n");
+            break;
+        }
+        bytesRead = offset;
+
+        // Create a new stream for the embedded codec
+        SkAutoTUnref<SkData> data(SkData::NewFromStream(stream, size));
+        if (NULL == data.get()) {
+            SkDebugf("Warning: could not create embedded stream.\n");
+            break;
+        }
+        SkAutoTDelete<SkMemoryStream>
+                embeddedStream(SkNEW_ARGS(SkMemoryStream, (data.get())));
+        bytesRead += size;
+
+        // Check if the embedded codec is bmp or png and create the codec
+        const bool isPng = SkPngCodec::IsPng(embeddedStream);
+        SkAssertResult(embeddedStream->rewind());
+        SkCodec* codec = NULL;
+        if (isPng) {
+            codec = SkPngCodec::NewFromStream(embeddedStream.detach());
+        } else {
+            codec = SkBmpCodec::NewFromIco(embeddedStream.detach());
+        }
+
+        // Save a valid codec
+        if (NULL != codec) {
+            codecs->push_back();
+            codecs->operator[](codecs->count() - 1).reset(codec);

[scroggo, 2015/03/23 20:34:51]

push_back returns a T&, so you can combine these two lines:

codecs->push_back().reset(codec);

[msarett, 2015/03/24 13:08:37]

Nice, that's convenient!

+        }
+    }
+
+    // Recognize if there are no valid codecs
+    if (0 == codecs->count()) {
+        SkDebugf("Error: could not find any valid embedded ico codecs.\n");
+        return NULL;
+    }
+
+    // Use the largest codec as a "suggestion" for image info
+    uint32_t maxSize = 0;
+    uint32_t maxIndex = 0;
+    for (int32_t i = 0; i < codecs->count(); i++) {
+        SkImageInfo info = codecs->operator[](i)->getInfo();
+        uint32_t size = info.width() * info.height();
+        if (size > maxSize) {
+            maxSize = size;
+            maxIndex = i;
+        }
+    }
+    SkImageInfo info = codecs->operator[](maxIndex)->getInfo();
+
+    // Note that stream is owned by the embedded codec, the ico does not need
+    // direct access to the stream.
+    return SkNEW_ARGS(SkIcoCodec, (info, codecs.detach()));
+}
+
+/*
+ * Creates an instance of the decoder
+ * Called only by NewFromStream
+ */
+SkIcoCodec::SkIcoCodec(const SkImageInfo& info,
+                       SkTArray<SkAutoTDelete<SkCodec>, true>* codecs)
+    : INHERITED(info, NULL)
+    , fEmbeddedCodecs(codecs)
+{}
+
+/*
+ * Chooses the best dimensions given the desired scale
+ */
+SkISize SkIcoCodec::onGetScaledDimensions(float desiredScale) const { 
+    // We set the dimensions to the largest candidate image by default.
+    // Regardless of the scale request, this is the largest image that we
+    // will decode.
+    if (desiredScale >= 1.0) {
+        return this->getInfo().dimensions();
+    }
+
+    int origWidth = this->getInfo().width();
+    int origHeight = this->getInfo().height();
+    float desiredSize = desiredScale * origWidth * origHeight;
+    // At least one image will have smaller error than this initial value
+    float minError = origWidth * origHeight - desiredSize + 1.0;
+    int32_t minIndex = -1;
+    for (int32_t i = 0; i < fEmbeddedCodecs->count(); i++) {
+        int width = fEmbeddedCodecs->operator[](i)->getInfo().width();
+        int height = fEmbeddedCodecs->operator[](i)->getInfo().height();
+        float error = SkTAbs(((float) (width * height)) - desiredSize);
+        if (error < minError) {
+            minError = error;
+            minIndex = i;
+        }
+    }
+    SkASSERT(minIndex >= 0);
+
+    return fEmbeddedCodecs->operator[](minIndex)->getInfo().dimensions();
+}
+
+/*
+ * Initiates the Ico decode
+ */
+SkCodec::Result SkIcoCodec::onGetPixels(const SkImageInfo& dstInfo,
+                                        void* dst, size_t dstRowBytes,
+                                        const Options& opts, SkPMColor* ct,
+                                        int* ptr) {
+    for (int32_t i = 0; i < fEmbeddedCodecs->count(); i++) {
+        // If the dimensions match, try to decode
+        if (dstInfo.dimensions() ==
+                fEmbeddedCodecs->operator[](i)->getInfo().dimensions()) {
+
+            // Perform the decode
+            Result result = fEmbeddedCodecs->operator[](i)->getPixels(dstInfo,
+                    dst, dstRowBytes, &opts, ct, ptr);
+
+            // On a fatal error, keep trying to find an image to decode
+            if (kInvalidConversion == result || kInvalidInput == result) {

[scroggo, 2015/03/23 20:34:51]

Why did you pick these two? I would think if we got kInvalidScale we'd want to
try again, too.

[msarett, 2015/03/24 13:08:37]

I absolutely agree.  I assumed that since we were checking dimensions
before-hand in this function, we would never get an invalid scale error.  But
the other implementations may change, so it can't hurt to check.

[scroggo, 2015/03/24 15:24:42]

Oh right, I wasn't thinking. I'm fine with or without the extra check.

+                SkDebugf("Warning: Attempt to decode candidate ico failed.\n");
+                continue;
+            }
+
+            // On success or partial success, return the result
+            return result;
+        }
+    }
+
+    SkDebugf("Error: No ico candidate image with matching dimensions.\n");
+    return kInvalidScale;
+}