[image_picker_android] Improved Bitmap resize on Android (flutter#3423)

Improves Bitmap load and resize on Android.

Original PR on flutter/plugins: flutter/plugins#6947

Issue: flutter#118383

Author: beroso

packages/image_picker/image_picker_android/AUTHORS

@@ -64,3 +64,4 @@ Aleksandr Yurkovskiy <sanekyy@gmail.com>
 Anton Borries <mail@antonborri.es>
 Alex Li <google@alexv525.com>
 Rahul Raj <64.rahulraj@gmail.com>
+André Sousa <andrelvsousa@gmail.com>

packages/image_picker/image_picker_android/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.8.6+12
+
+* Improves image resizing performance by decoding Bitmap only when needed.
+
 ## 0.8.6+11
 
 * Updates gradle to 7.6.1.

packages/image_picker/image_picker_android/android/src/main/java/io/flutter/plugins/imagepicker/ImageResizer.java

@@ -7,7 +7,9 @@
 import android.graphics.Bitmap;
 import android.graphics.BitmapFactory;
 import android.util.Log;
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.core.util.SizeFCompat;
 import java.io.ByteArrayOutputStream;
 import java.io.File;
 import java.io.FileOutputStream;
@@ -30,8 +32,8 @@ class ImageResizer {
    */
   String resizeImageIfNeeded(
       String imagePath, @Nullable Double maxWidth, @Nullable Double maxHeight, int imageQuality) {
-    Bitmap bmp = decodeFile(imagePath);
-    if (bmp == null) {
+    SizeFCompat originalSize = readFileDimensions(imagePath);
+    if (originalSize.getWidth() == -1 || originalSize.getHeight() == -1) {
       return imagePath;
     }
     boolean shouldScale = maxWidth != null || maxHeight != null || imageQuality < 100;
@@ -41,7 +43,26 @@ String resizeImageIfNeeded(
     try {
       String[] pathParts = imagePath.split("/");
       String imageName = pathParts[pathParts.length - 1];
-      File file = resizedImage(bmp, maxWidth, maxHeight, imageQuality, imageName);
+      SizeFCompat targetSize =
+          calculateTargetSize(
+              (double) originalSize.getWidth(),
+              (double) originalSize.getHeight(),
+              maxWidth,
+              maxHeight);
+      BitmapFactory.Options options = new BitmapFactory.Options();
+      options.inSampleSize =
+          calculateSampleSize(options, (int) targetSize.getWidth(), (int) targetSize.getHeight());
+      Bitmap bmp = decodeFile(imagePath, options);
+      if (bmp == null) {
+        return imagePath;
+      }
+      File file =
+          resizedImage(
+              bmp,
+              (double) targetSize.getWidth(),
+              (double) targetSize.getHeight(),
+              imageQuality,
+              imageName);
       copyExif(imagePath, file.getPath());
       return file.getPath();
     } catch (IOException e) {
@@ -50,10 +71,19 @@ String resizeImageIfNeeded(
   }
 
   private File resizedImage(
-      Bitmap bmp, Double maxWidth, Double maxHeight, int imageQuality, String outputImageName)
+      Bitmap bmp, Double width, Double height, int imageQuality, String outputImageName)
       throws IOException {
-    double originalWidth = bmp.getWidth() * 1.0;
-    double originalHeight = bmp.getHeight() * 1.0;
+    Bitmap scaledBmp = createScaledBitmap(bmp, width.intValue(), height.intValue(), false);
+    File file =
+        createImageOnExternalDirectory("/scaled_" + outputImageName, scaledBmp, imageQuality);
+    return file;
+  }
+
+  private SizeFCompat calculateTargetSize(
+      @NonNull Double originalWidth,
+      @NonNull Double originalHeight,
+      @Nullable Double maxWidth,
+      @Nullable Double maxHeight) {
 
     boolean hasMaxWidth = maxWidth != null;
     boolean hasMaxHeight = maxHeight != null;
@@ -90,10 +120,7 @@ private File resizedImage(
       }
     }
 
-    Bitmap scaledBmp = createScaledBitmap(bmp, width.intValue(), height.intValue(), false);
-    File file =
-        createImageOnExternalDirectory("/scaled_" + outputImageName, scaledBmp, imageQuality);
-    return file;
+    return new SizeFCompat(width.floatValue(), height.floatValue());
   }
 
   private File createFile(File externalFilesDirectory, String child) {
@@ -112,14 +139,47 @@ private void copyExif(String filePathOri, String filePathDest) {
     exifDataCopier.copyExif(filePathOri, filePathDest);
   }
 
-  private Bitmap decodeFile(String path) {
-    return BitmapFactory.decodeFile(path);
+  private SizeFCompat readFileDimensions(String path) {
+    BitmapFactory.Options options = new BitmapFactory.Options();
+    options.inJustDecodeBounds = true;
+    decodeFile(path, options);
+    return new SizeFCompat(options.outWidth, options.outHeight);
+  }
+
+  private Bitmap decodeFile(String path, @Nullable BitmapFactory.Options opts) {
+    return BitmapFactory.decodeFile(path, opts);
   }
 
   private Bitmap createScaledBitmap(Bitmap bmp, int width, int height, boolean filter) {
     return Bitmap.createScaledBitmap(bmp, width, height, filter);
   }
 
+  /**
+   * Calculates the largest sample size value that is a power of two based on a target width and
+   * height.
+   *
+   * <p>This value is necessary to tell the Bitmap decoder to subsample the original image,
+   * returning a smaller image to save memory.
+   *
+   * @see <a
+   *     href="https://developer.android.com/topic/performance/graphics/load-bitmap#load-bitmap">
+   *     Loading Large Bitmaps Efficiently</a>
+   */
+  private int calculateSampleSize(
+      BitmapFactory.Options options, int targetWidth, int targetHeight) {
+    final int height = options.outHeight;
+    final int width = options.outWidth;
+    int sampleSize = 1;
+    if (height > targetHeight || width > targetWidth) {
+      final int halfHeight = height / 2;
+      final int halfWidth = width / 2;
+      while ((halfHeight / sampleSize) >= targetHeight && (halfWidth / sampleSize) >= targetWidth) {
+        sampleSize *= 2;
+      }
+    }
+    return sampleSize;
+  }
+
   private File createImageOnExternalDirectory(String name, Bitmap bitmap, int imageQuality)
       throws IOException {
     ByteArrayOutputStream outputStream = new ByteArrayOutputStream();

packages/image_picker/image_picker_android/android/src/test/java/io/flutter/plugins/imagepicker/ImageResizerTest.java

@@ -6,17 +6,24 @@
 
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.core.IsEqual.equalTo;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.times;
 
 import android.graphics.Bitmap;
 import android.graphics.BitmapFactory;
 import java.io.File;
 import java.io.IOException;
+import java.util.List;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
 import org.junit.runner.RunWith;
+import org.mockito.ArgumentCaptor;
 import org.mockito.MockedStatic;
 import org.mockito.Mockito;
 import org.mockito.MockitoAnnotations;
@@ -102,4 +109,32 @@ public void onResizeImageIfNeeded_whenImagePathIsNotBitmap_shouldReturnPathAndNo
       assertThat(resizedImagePath, equalTo(nonBitmapImagePath));
     }
   }
+
+  @Test
+  public void onResizeImageIfNeeded_whenResizeIsNotNecessary_shouldOnlyQueryBitmapDimensions() {
+    try (MockedStatic<BitmapFactory> mockBitmapFactory =
+        mockStatic(BitmapFactory.class, Mockito.CALLS_REAL_METHODS)) {
+      String outputFile = resizer.resizeImageIfNeeded(imageFile.getPath(), null, null, 100);
+      ArgumentCaptor<BitmapFactory.Options> argument =
+          ArgumentCaptor.forClass(BitmapFactory.Options.class);
+      mockBitmapFactory.verify(() -> BitmapFactory.decodeFile(anyString(), argument.capture()));
+      BitmapFactory.Options capturedOptions = argument.getValue();
+      assertTrue(capturedOptions.inJustDecodeBounds);
+    }
+  }
+
+  @Test
+  public void onResizeImageIfNeeded_whenResizeIsNecessary_shouldDecodeBitmapPixels() {
+    try (MockedStatic<BitmapFactory> mockBitmapFactory =
+        mockStatic(BitmapFactory.class, Mockito.CALLS_REAL_METHODS)) {
+      String outputFile = resizer.resizeImageIfNeeded(imageFile.getPath(), 50.0, 50.0, 100);
+      ArgumentCaptor<BitmapFactory.Options> argument =
+          ArgumentCaptor.forClass(BitmapFactory.Options.class);
+      mockBitmapFactory.verify(
+          () -> BitmapFactory.decodeFile(anyString(), argument.capture()), times(2));
+      List<BitmapFactory.Options> capturedOptions = argument.getAllValues();
+      assertTrue(capturedOptions.get(0).inJustDecodeBounds);
+      assertFalse(capturedOptions.get(1).inJustDecodeBounds);
+    }
+  }
 }

packages/image_picker/image_picker_android/pubspec.yaml

@@ -3,7 +3,7 @@ description: Android implementation of the image_picker plugin.
 repository: https://github.com/flutter/packages/tree/main/packages/image_picker/image_picker_android
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+image_picker%22
 
-version: 0.8.6+11
+version: 0.8.6+12
 
 environment:
   sdk: ">=2.18.0 <4.0.0"