234 lines
8.8 KiB
Java
234 lines
8.8 KiB
Java
/*
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* Copyright (C) 2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License
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*/
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package com.android.internal.util;
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import android.content.ContentProviderClient;
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import android.content.ContentResolver;
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import android.graphics.Bitmap;
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import android.graphics.Bitmap.Config;
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import android.graphics.Canvas;
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import android.graphics.ImageDecoder;
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import android.graphics.ImageDecoder.ImageInfo;
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import android.graphics.ImageDecoder.Source;
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import android.graphics.Matrix;
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import android.graphics.Paint;
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import android.graphics.Point;
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import android.graphics.PorterDuff;
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import android.graphics.drawable.BitmapDrawable;
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import android.graphics.drawable.Drawable;
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import android.net.Uri;
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import android.os.Bundle;
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import android.util.Size;
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import java.io.IOException;
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/**
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* Utility class for image analysis and processing.
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*
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* @hide
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*/
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public class ImageUtils {
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// Amount (max is 255) that two channels can differ before the color is no longer "gray".
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private static final int TOLERANCE = 20;
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// Alpha amount for which values below are considered transparent.
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private static final int ALPHA_TOLERANCE = 50;
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// Size of the smaller bitmap we're actually going to scan.
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private static final int COMPACT_BITMAP_SIZE = 64; // pixels
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private int[] mTempBuffer;
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private Bitmap mTempCompactBitmap;
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private Canvas mTempCompactBitmapCanvas;
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private Paint mTempCompactBitmapPaint;
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private final Matrix mTempMatrix = new Matrix();
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/**
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* Checks whether a bitmap is grayscale. Grayscale here means "very close to a perfect
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* gray".
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*
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* Instead of scanning every pixel in the bitmap, we first resize the bitmap to no more than
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* COMPACT_BITMAP_SIZE^2 pixels using filtering. The hope is that any non-gray color elements
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* will survive the squeezing process, contaminating the result with color.
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*/
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public boolean isGrayscale(Bitmap bitmap) {
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int height = bitmap.getHeight();
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int width = bitmap.getWidth();
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// shrink to a more manageable (yet hopefully no more or less colorful) size
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if (height > COMPACT_BITMAP_SIZE || width > COMPACT_BITMAP_SIZE) {
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if (mTempCompactBitmap == null) {
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mTempCompactBitmap = Bitmap.createBitmap(
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COMPACT_BITMAP_SIZE, COMPACT_BITMAP_SIZE, Bitmap.Config.ARGB_8888
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);
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mTempCompactBitmapCanvas = new Canvas(mTempCompactBitmap);
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mTempCompactBitmapPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
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mTempCompactBitmapPaint.setFilterBitmap(true);
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}
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mTempMatrix.reset();
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mTempMatrix.setScale(
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(float) COMPACT_BITMAP_SIZE / width,
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(float) COMPACT_BITMAP_SIZE / height,
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0, 0);
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mTempCompactBitmapCanvas.drawColor(0, PorterDuff.Mode.SRC); // select all, erase
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mTempCompactBitmapCanvas.drawBitmap(bitmap, mTempMatrix, mTempCompactBitmapPaint);
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bitmap = mTempCompactBitmap;
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width = height = COMPACT_BITMAP_SIZE;
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}
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final int size = height * width;
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ensureBufferSize(size);
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bitmap.getPixels(mTempBuffer, 0, width, 0, 0, width, height);
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for (int i = 0; i < size; i++) {
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if (!isGrayscale(mTempBuffer[i])) {
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return false;
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}
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}
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return true;
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}
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/**
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* Makes sure that {@code mTempBuffer} has at least length {@code size}.
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*/
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private void ensureBufferSize(int size) {
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if (mTempBuffer == null || mTempBuffer.length < size) {
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mTempBuffer = new int[size];
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}
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}
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/**
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* Classifies a color as grayscale or not. Grayscale here means "very close to a perfect
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* gray"; if all three channels are approximately equal, this will return true.
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*
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* Note that really transparent colors are always grayscale.
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*/
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public static boolean isGrayscale(int color) {
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int alpha = 0xFF & (color >> 24);
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if (alpha < ALPHA_TOLERANCE) {
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return true;
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}
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int r = 0xFF & (color >> 16);
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int g = 0xFF & (color >> 8);
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int b = 0xFF & color;
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return Math.abs(r - g) < TOLERANCE
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&& Math.abs(r - b) < TOLERANCE
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&& Math.abs(g - b) < TOLERANCE;
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}
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/**
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* Convert a drawable to a bitmap, scaled to fit within maxWidth and maxHeight.
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*/
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public static Bitmap buildScaledBitmap(Drawable drawable, int maxWidth,
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int maxHeight) {
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return buildScaledBitmap(drawable, maxWidth, maxHeight, false);
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}
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/**
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* Convert a drawable to a bitmap, scaled to fit within maxWidth and maxHeight.
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*
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* @param allowUpscaling if true, the drawable will not only be scaled down, but also scaled up
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* to fit within the maximum size given. This is useful for converting
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* vectorized icons which usually have a very small intrinsic size.
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*/
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public static Bitmap buildScaledBitmap(Drawable drawable, int maxWidth,
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int maxHeight, boolean allowUpscaling) {
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if (drawable == null) {
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return null;
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}
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int originalWidth = drawable.getIntrinsicWidth();
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int originalHeight = drawable.getIntrinsicHeight();
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if ((originalWidth <= maxWidth) && (originalHeight <= maxHeight) &&
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(drawable instanceof BitmapDrawable)) {
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return ((BitmapDrawable) drawable).getBitmap();
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}
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if (originalHeight <= 0 || originalWidth <= 0) {
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return null;
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}
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// create a new bitmap, scaling down to fit the max dimensions of
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// a large notification icon if necessary
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float ratio = Math.min((float) maxWidth / (float) originalWidth,
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(float) maxHeight / (float) originalHeight);
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if (!allowUpscaling) {
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ratio = Math.min(1.0f, ratio);
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}
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int scaledWidth = (int) (ratio * originalWidth);
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int scaledHeight = (int) (ratio * originalHeight);
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Bitmap result = Bitmap.createBitmap(scaledWidth, scaledHeight, Config.ARGB_8888);
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// and paint our app bitmap on it
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Canvas canvas = new Canvas(result);
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drawable.setBounds(0, 0, scaledWidth, scaledHeight);
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drawable.draw(canvas);
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return result;
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}
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/**
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* @see https://developer.android.com/topic/performance/graphics/load-bitmap
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*/
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public static int calculateSampleSize(Size currentSize, Size requestedSize) {
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int inSampleSize = 1;
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if (currentSize.getHeight() > requestedSize.getHeight()
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|| currentSize.getWidth() > requestedSize.getWidth()) {
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final int halfHeight = currentSize.getHeight() / 2;
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final int halfWidth = currentSize.getWidth() / 2;
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// Calculate the largest inSampleSize value that is a power of 2 and keeps both
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// height and width larger than the requested height and width.
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while ((halfHeight / inSampleSize) >= requestedSize.getHeight()
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&& (halfWidth / inSampleSize) >= requestedSize.getWidth()) {
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inSampleSize *= 2;
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}
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}
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return inSampleSize;
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}
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/**
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* Load a bitmap, and attempt to downscale to the required size, to save
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* on memory. Updated to use newer and more compatible ImageDecoder.
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*
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* @see https://developer.android.com/topic/performance/graphics/load-bitmap
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*/
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public static Bitmap loadThumbnail(ContentResolver resolver, Uri uri, Size size)
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throws IOException {
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try (ContentProviderClient client = resolver.acquireContentProviderClient(uri)) {
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final Bundle opts = new Bundle();
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opts.putParcelable(ContentResolver.EXTRA_SIZE,
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new Point(size.getWidth(), size.getHeight()));
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return ImageDecoder.decodeBitmap(ImageDecoder.createSource(() -> {
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return client.openTypedAssetFile(uri, "image/*", opts, null);
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}), (ImageDecoder decoder, ImageInfo info, Source source) -> {
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decoder.setAllocator(ImageDecoder.ALLOCATOR_SOFTWARE);
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final int sample = calculateSampleSize(info.getSize(), size);
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if (sample > 1) {
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decoder.setTargetSampleSize(sample);
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}
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});
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}
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}
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}
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