Media Galleries API Metadata: Image metadata

chrome/utility/media_galleries/image_metadata_extractor.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/utility/media_galleries/image_metadata_extractor.h"
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "base/numerics/safe_conversions.h"
+#include "base/strings/string_number_conversions.h"
+#include "media/base/data_source.h"
+#include "net/base/io_buffer.h"
+
+extern "C" {
+#include <libexif/exif-data.h>
+}  // extern "C"
+
+namespace metadata {
+
+namespace {
+
+const int kMaxBufferSize = 50 * 1024 * 1024;  // Arbitrary maximum of 50MB.
+
+void FinishGetImageBytes(
+    net::DrainableIOBuffer* buffer,
+    media::DataSource* source,
+    const base::Callback<void(net::DrainableIOBuffer*)>& callback,
+    int bytes_read) {
+  if (bytes_read == media::DataSource::kReadError) {
+    callback.Run(NULL);
+    return;
+  }
+
+  buffer->DidConsume(bytes_read);
+  // Didn't get the whole file. Continue reading to get the rest.
+  if (buffer->BytesRemaining() > 0) {
+    source->Read(0, buffer->BytesRemaining(), (uint8*)buffer->data(),
+                 base::Bind(&FinishGetImageBytes, make_scoped_refptr(buffer),
+                            base::Unretained(source), callback));
+    return;
+  }
+
+  buffer->SetOffset(0);
+  callback.Run(make_scoped_refptr(buffer));
+}
+
+void GetImageBytes(
+    media::DataSource* source,
+    const base::Callback<void(net::DrainableIOBuffer*)>& callback) {
+  int64 size64 = 0;
+  if (!source->GetSize(&size64) || size64 > kMaxBufferSize)
+    return callback.Run(NULL);
+  int size = base::checked_cast<int>(size64);
+
+  scoped_refptr<net::DrainableIOBuffer> buffer(
+      new net::DrainableIOBuffer(new net::IOBuffer(size), size));
+  source->Read(0, buffer->BytesRemaining(), (uint8*)buffer->data(),
+               base::Bind(&FinishGetImageBytes, buffer,
+                          base::Unretained(source), callback));
+}
+
+void ExtractInt(ExifData* data, ExifTag tag, int* result) {
+  DCHECK(result);
+
+  ExifEntry* entry = exif_data_get_entry(data, tag);
+
+  if (entry) {
+    ExifByteOrder order = exif_data_get_byte_order(data);
+
+    switch (entry->format) {
+      case EXIF_FORMAT_SHORT: {
+        ExifShort v = exif_get_short(entry->data, order);
+        *result = base::checked_cast<int>(v);
+        break;
+      }
+      case EXIF_FORMAT_LONG: {
+        ExifLong v = exif_get_long(entry->data, order);
+        // Ignore values that don't fit in a signed int - probably invalid data.
+        if (base::IsValueInRangeForNumericType<int>(v))
+          *result = base::checked_cast<int>(v);
+        break;
+      }
+      default: {
+        // Ignore all other entry formats.
+      }
+    }
+  }
+}
+
+void ExtractDouble(ExifData* data, ExifTag tag, double* result) {
+  DCHECK(result);
+
+  ExifEntry* entry = exif_data_get_entry(data, tag);
+
+  if (entry) {
+    ExifByteOrder order = exif_data_get_byte_order(data);
+
+    if (entry->format == EXIF_FORMAT_RATIONAL) {
+      ExifRational v = exif_get_rational(entry->data, order);
+      *result = base::checked_cast<double>(v.numerator) /
+          base::checked_cast<double>(v.denominator);
+    }
+  }
+}
+
+void ExtractString(ExifData* data, ExifTag tag, std::string* result) {
+  DCHECK(result);
+
+  ExifEntry* entry = exif_data_get_entry(data, tag);
+
+  if (entry) {
+    char buf[1024];
+    exif_entry_get_value(entry, buf, sizeof(buf));
+    *result = buf;
+  }
+}
+
+}  // namespace
+
+ImageMetadataExtractor::ImageMetadataExtractor()
+    : extracted_(false),
+      width_(-1),
+      height_(-1),
+      rotation_(-1),
+      x_resolution_(-1),
+      y_resolution_(-1),
+      exposure_time_sec_(-1),
+      flash_fired_(false),
+      f_number_(-1),
+      focal_length_mm_(-1),
+      iso_equivalent_(-1) {
+}
+
+ImageMetadataExtractor::~ImageMetadataExtractor() {
+}
+
+void ImageMetadataExtractor::Extract(media::DataSource* source,
+                                     const DoneCallback& callback) {
+  DCHECK(!extracted_);
+
+  GetImageBytes(source, base::Bind(&ImageMetadataExtractor::FinishExtraction,
+                                   base::Unretained(this), callback));
+
+}
+
+int ImageMetadataExtractor::width() const {
+  DCHECK(extracted_);
+  return width_;
+}
+
+int ImageMetadataExtractor::height() const {
+  DCHECK(extracted_);
+  return height_;
+}
+
+int ImageMetadataExtractor::rotation() const {
+  DCHECK(extracted_);
+  return rotation_;
+}
+
+double ImageMetadataExtractor::x_resolution() const {
+  DCHECK(extracted_);
+  return x_resolution_;
+}
+
+double ImageMetadataExtractor::y_resolution() const {
+  DCHECK(extracted_);
+  return y_resolution_;
+}
+
+const std::string& ImageMetadataExtractor::date() const {
+  DCHECK(extracted_);
+  return date_;
+}
+
+const std::string& ImageMetadataExtractor::camera_make() const {
+  DCHECK(extracted_);
+  return camera_make_;
+}
+
+const std::string& ImageMetadataExtractor::camera_model() const {
+  DCHECK(extracted_);
+  return camera_model_;
+}
+
+double ImageMetadataExtractor::exposure_time_sec() const {
+  DCHECK(extracted_);
+  return exposure_time_sec_;
+}
+
+bool ImageMetadataExtractor::flash_fired() const {
+  DCHECK(extracted_);
+  return flash_fired_;
+}
+
+double ImageMetadataExtractor::f_number() const {
+  DCHECK(extracted_);
+  return f_number_;
+}
+
+double ImageMetadataExtractor::focal_length_mm() const {
+  DCHECK(extracted_);
+  return focal_length_mm_;
+}
+
+int ImageMetadataExtractor::iso_equivalent() const {
+  DCHECK(extracted_);
+  return iso_equivalent_;
+}
+
+void ImageMetadataExtractor::FinishExtraction(
+    const DoneCallback& callback, net::DrainableIOBuffer* buffer) {
+  if (!buffer) {
+    callback.Run(false);
+    return;
+  }
+
+  ExifData* data = exif_data_new_from_data(
+      (unsigned char*)buffer->data(), buffer->BytesRemaining());
+
+  if (!data) {
+    callback.Run(false);
+    return;
+  }
+
+  ExtractInt(data, EXIF_TAG_IMAGE_WIDTH, &width_);
+  ExtractInt(data, EXIF_TAG_IMAGE_LENGTH, &height_);
+
+  // We ignore the mirrored-aspect of the mirrored-orientations and just
+  // indicate the rotation. Mirrored-orientations are very rare.
+  int orientation = 0;
+  ExtractInt(data, EXIF_TAG_ORIENTATION, &orientation);
+  switch (orientation) {
+    case 1:
+    case 2:
+      rotation_ = 0;
+      break;
+    case 3:
+    case 4:
+      rotation_ = 180;
+      break;
+    case 5:
+    case 6:
+      rotation_ = 90;
+      break;
+    case 7:
+    case 8:
+      rotation_ = 270;
+      break;
+  }
+
+  ExtractDouble(data, EXIF_TAG_X_RESOLUTION, &x_resolution_);
+  ExtractDouble(data, EXIF_TAG_Y_RESOLUTION, &y_resolution_);
+
+  ExtractString(data, EXIF_TAG_DATE_TIME, &date_);
+
+  ExtractString(data, EXIF_TAG_MAKE, &camera_make_);
+  ExtractString(data, EXIF_TAG_MODEL, &camera_model_);
+  ExtractDouble(data, EXIF_TAG_EXPOSURE_TIME, &exposure_time_sec_);
+
+  int flash_value = -1;
+  ExtractInt(data, EXIF_TAG_FLASH, &flash_value);
+  if (flash_value >= 0) {
+    flash_fired_ = (flash_value & 0x1) != 0;
+  }
+
+  ExtractDouble(data, EXIF_TAG_FNUMBER, &f_number_);
+  ExtractDouble(data, EXIF_TAG_FOCAL_LENGTH, &focal_length_mm_);
+  ExtractInt(data, EXIF_TAG_ISO_SPEED_RATINGS, &iso_equivalent_);
+
+  exif_data_free(data);
+
+  extracted_ = true;
+
+  callback.Run(true);
+}
+
+}  // namespace metadata