Specify scale type for glide thumbnails.

app/src/main/java/org/signal/glide/transforms/SignalDownsampleStrategy.kt

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2023 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+package org.signal.glide.transforms
+
+import com.bumptech.glide.load.resource.bitmap.DownsampleStrategy
+import kotlin.math.max
+import kotlin.math.min
+
+object SignalDownsampleStrategy {
+  /**
+   * Center outside, but don't up-scale, only downscale. You should be setting centerOutside
+   * on the target image view to still maintain center outside behavior.
+   */
+  @JvmField
+  val CENTER_OUTSIDE_NO_UPSCALE: DownsampleStrategy = CenterOutsideNoUpscale()
+
+  private class CenterOutsideNoUpscale : DownsampleStrategy() {
+    override fun getScaleFactor(
+      sourceWidth: Int,
+      sourceHeight: Int,
+      requestedWidth: Int,
+      requestedHeight: Int
+    ): Float {
+      val widthPercentage = requestedWidth / sourceWidth.toFloat()
+      val heightPercentage = requestedHeight / sourceHeight.toFloat()
+      return min(MAX_SCALE_FACTOR, max(widthPercentage, heightPercentage))
+    }
+
+    override fun getSampleSizeRounding(
+      sourceWidth: Int,
+      sourceHeight: Int,
+      requestedWidth: Int,
+      requestedHeight: Int
+    ): SampleSizeRounding {
+      return SampleSizeRounding.QUALITY
+    }
+
+    companion object {
+      private const val MAX_SCALE_FACTOR = 1f
+    }
+  }
+}