Improve loading big images

Load a scaled down bitmap instead of trying to load the
whole image and then scaling it down. If the image is too
large, it cannot be loaded completely in the first place.

app/src/main/kotlin/de/markusfisch/android/binaryeye/activity/PickActivity.kt

@@ -6,7 +6,6 @@ import android.graphics.Rect
 import android.net.Uri
 import android.os.Bundle
 import android.os.Parcelable
-import android.provider.MediaStore
 import android.support.v7.app.AppCompatActivity
 import android.support.v7.widget.Toolbar
 import android.view.Menu
@@ -19,10 +18,9 @@ import de.markusfisch.android.binaryeye.app.initSystemBars
 import de.markusfisch.android.binaryeye.app.setWindowInsetListener
 import de.markusfisch.android.binaryeye.app.setupInsets
 import de.markusfisch.android.binaryeye.graphics.crop
-import de.markusfisch.android.binaryeye.graphics.downsizeIfBigger
+import de.markusfisch.android.binaryeye.graphics.loadImageUri
 import de.markusfisch.android.binaryeye.widget.CropImageView
 import de.markusfisch.android.binaryeye.zxing.Zxing
-import java.io.IOException
 import kotlin.math.max
 import kotlin.math.min
 
@@ -143,21 +141,12 @@ class PickActivity : AppCompatActivity() {
 		val uri = intent.getParcelableExtra<Parcelable>(
 			Intent.EXTRA_STREAM
 		) as? Uri ?: return null
-		return loadImageUri(uri)
+		return loadImageUri(contentResolver, uri)
 	}
 
 	private fun loadImageToOpen(intent: Intent): Bitmap? {
 		val uri = intent.data ?: return null
-		return loadImageUri(uri)
-	}
-
-	private fun loadImageUri(uri: Uri): Bitmap? = try {
-		downsizeIfBigger(
-			MediaStore.Images.Media.getBitmap(contentResolver, uri),
-			1024
-		)
-	} catch (e: IOException) {
-		null
+		return loadImageUri(contentResolver, uri)
 	}
 
 	private fun scanImage(result: Result?) {

app/src/main/kotlin/de/markusfisch/android/binaryeye/graphics/BitmapEditor.kt

@@ -1,28 +1,52 @@
 package de.markusfisch.android.binaryeye.graphics
 
+import android.content.ContentResolver
 import android.graphics.Bitmap
+import android.graphics.BitmapFactory
 import android.graphics.Matrix
 import android.graphics.RectF
-import kotlin.math.max
+import android.net.Uri
+import java.io.IOException
 import kotlin.math.roundToInt
 
-fun downsizeIfBigger(bitmap: Bitmap, maxSize: Int): Bitmap = if (
-	max(bitmap.width, bitmap.height) > maxSize
-) {
-	val srcWidth = bitmap.width
-	val srcHeight = bitmap.height
-	var newWidth = maxSize
-	var newHeight = maxSize
-	if (srcWidth > srcHeight) {
-		newHeight = (newWidth.toFloat() / srcWidth.toFloat() *
-				srcHeight.toFloat()).roundToInt()
-	} else {
-		newWidth = (newHeight.toFloat() / srcHeight.toFloat() *
-				srcWidth.toFloat()).roundToInt()
+fun loadImageUri(cr: ContentResolver, uri: Uri): Bitmap? = try {
+	val options = BitmapFactory.Options()
+	cr.openInputStream(uri)?.use {
+		options.inJustDecodeBounds = true
+		BitmapFactory.decodeStream(it, null, options)
+		options.inSampleSize = calculateInSampleSize(
+			options.outWidth,
+			options.outHeight,
+			1024,
+			1024
+		)
+		options.inJustDecodeBounds = false
 	}
-	Bitmap.createScaledBitmap(bitmap, newWidth, newHeight, true)
-} else {
-	bitmap
+	cr.openInputStream(uri)?.use {
+		BitmapFactory.decodeStream(it, null, options)
+	}
+} catch (e: IOException) {
+	null
+}
+
+private fun calculateInSampleSize(
+	width: Int,
+	height: Int,
+	reqWidth: Int,
+	reqHeight: Int
+): Int {
+	var inSampleSize = 1
+	if (height > reqHeight || width > reqWidth) {
+		val halfHeight = height / 2
+		val halfWidth = width / 2
+		while (
+			halfHeight / inSampleSize >= reqHeight ||
+			halfWidth / inSampleSize >= reqWidth
+		) {
+			inSampleSize *= 2
+		}
+	}
+	return inSampleSize
 }
 
 fun crop(bitmap: Bitmap, rect: RectF, rotation: Float) = try {