fix(study-options): load local images in deck description

AnkiDroid/src/main/java/com/ichi2/anki/StudyOptionsFragment.kt

@@ -16,6 +16,7 @@ package com.ichi2.anki
 import android.app.Activity
 import android.content.Intent
 import android.os.Bundle
+import android.text.Html
 import android.text.Spanned
 import android.text.method.LinkMovementMethod
 import android.view.LayoutInflater
@@ -32,6 +33,7 @@ import androidx.annotation.VisibleForTesting
 import androidx.constraintlayout.widget.Group
 import androidx.core.os.bundleOf
 import androidx.core.text.HtmlCompat
+import androidx.core.text.parseAsHtml
 import androidx.core.view.MenuProvider
 import androidx.core.view.isVisible
 import androidx.fragment.app.Fragment
@@ -51,6 +53,7 @@ import com.ichi2.anki.reviewreminders.ScheduleReminders
 import com.ichi2.anki.settings.Prefs
 import com.ichi2.anki.ui.internationalization.toSentenceCase
 import com.ichi2.anki.utils.ext.showDialogFragment
+import com.ichi2.ui.CollectionMediaImageGetter
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
@@ -459,7 +462,16 @@ class StudyOptionsFragment :
                 }
             }
         if (desc.isNotEmpty()) {
-            textDeckDescription.text = formatDescription(desc)
+            val mediaDir = col.media.dir
+            val imageGetter =
+                CollectionMediaImageGetter(
+                    requireContext(),
+                    textDeckDescription,
+                    mediaDir,
+                    viewLifecycleOwner.lifecycleScope,
+                )
+
+            textDeckDescription.text = formatDescription(desc, imageGetter)
             textDeckDescription.visibility = View.VISIBLE
         } else {
             textDeckDescription.visibility = View.GONE
@@ -540,14 +552,19 @@ class StudyOptionsFragment :
         @VisibleForTesting
         fun formatDescription(
             @Language("HTML") desc: String,
+            imageGetter: Html.ImageGetter? = null,
         ): Spanned {
             // #5715: In deck description, ignore what is in style and script tag
             // Since we don't currently execute the JS/CSS, it's not worth displaying.
             val withStrippedTags = stripHTMLScriptAndStyleTags(desc)
             // #5188 - compat.fromHtml converts newlines into spaces.
             val withoutWindowsLineEndings = withStrippedTags.replace("\r\n", "<br/>")
             val withoutLinuxLineEndings = withoutWindowsLineEndings.replace("\n", "<br/>")
-            return HtmlCompat.fromHtml(withoutLinuxLineEndings, HtmlCompat.FROM_HTML_MODE_LEGACY)
+
+            return withoutLinuxLineEndings.parseAsHtml(
+                flags = HtmlCompat.FROM_HTML_MODE_LEGACY,
+                imageGetter = imageGetter,
+            )
         }
     }
 

AnkiDroid/src/main/java/com/ichi2/ui/CollectionMediaImageGetter.kt

@@ -0,0 +1,182 @@
+/*
+ * Copyright (c) 2025 Rakshita Chauhan <chauhanrakshita64@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package com.ichi2.ui
+
+import android.content.Context
+import android.graphics.Bitmap
+import android.graphics.BitmapFactory
+import android.graphics.Color
+import android.graphics.drawable.Drawable
+import android.graphics.drawable.LevelListDrawable
+import android.text.Html
+import android.widget.TextView
+import androidx.annotation.CheckResult
+import androidx.core.graphics.drawable.toDrawable
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import timber.log.Timber
+import java.io.File
+import java.lang.ref.WeakReference
+
+/**
+ * Async ImageGetter for Deck Descriptions.
+ * Resolves local images from the collection media directory and downsamples them to prevent OOM.
+ */
+class CollectionMediaImageGetter(
+    private val context: Context,
+    view: TextView,
+    private val mediaDir: File,
+    private val scope: CoroutineScope,
+) : Html.ImageGetter {
+    private val containerRef = WeakReference(view)
+
+    override fun getDrawable(source: String): Drawable {
+        // Return a transparent placeholder
+        val wrapper = createWrapper()
+
+        scope.launch {
+            val bitmap = loadBitmap(source) ?: return@launch
+            updateWrapper(wrapper, bitmap)
+        }
+
+        return wrapper
+    }
+
+    private fun createWrapper(): LevelListDrawable {
+        val wrapper = LevelListDrawable()
+        val empty = Color.TRANSPARENT.toDrawable()
+        wrapper.addLevel(0, 0, empty)
+        wrapper.setBounds(0, 0, 0, 0)
+        return wrapper
+    }
+
+    @CheckResult
+    private suspend fun loadBitmap(source: String): Bitmap? =
+        withContext(Dispatchers.IO) {
+            try {
+                // Skip remote images
+                if (source.startsWith("http://") || source.startsWith("https://")) {
+                    return@withContext null
+                }
+
+                val localFile = File(mediaDir, source)
+
+                // Prevent path traversal to ensure file is inside media directory
+                if (!localFile.canonicalPath.startsWith(mediaDir.canonicalPath)) {
+                    return@withContext null
+                }
+
+                if (localFile.exists()) {
+                    // Use view width or fallback to screen width
+                    val reqWidth =
+                        (containerRef.get()?.width ?: 0)
+                            .coerceAtLeast(context.resources.displayMetrics.widthPixels)
+                    decodeSampledBitmap(localFile, reqWidth)
+                } else {
+                    null
+                }
+            } catch (e: Throwable) {
+                Timber.Forest.w(e, "Failed to load deck description image: %s", source)
+                null
+            }
+        }
+
+    private fun updateWrapper(
+        wrapper: LevelListDrawable,
+        bitmap: Bitmap,
+    ) {
+        val textView = containerRef.get()
+
+        if (textView == null) {
+            Timber.w("CollectionMediaImageGetter: TextView reference lost")
+            return
+        }
+
+        val d = bitmap.toDrawable(context.resources)
+
+        var viewWidth = textView.width
+        if (viewWidth <= 0) viewWidth = context.resources.displayMetrics.widthPixels
+
+        val scale = viewWidth.toFloat() / bitmap.width
+        var w = bitmap.width
+        var h = bitmap.height
+
+        // Downscale to fit view if necessary
+        if (scale < 1.0f) {
+            w = viewWidth
+            h = (h * scale).toInt()
+        }
+
+        d.setBounds(0, 0, w, h)
+        wrapper.addLevel(1, 1, d)
+        wrapper.setBounds(0, 0, w, h)
+        wrapper.level = 1
+
+        textView.text = textView.text
+    }
+
+    companion object {
+        /**
+         * Decodes a file, downsampling it to fit within the reqWidth.
+         */
+        @CheckResult
+        fun decodeSampledBitmap(
+            file: File,
+            reqWidth: Int,
+        ): Bitmap? {
+            // First decode with inJustDecodeBounds=true to check dimensions
+            val options = BitmapFactory.Options()
+            options.inJustDecodeBounds = true
+            BitmapFactory.decodeFile(file.absolutePath, options)
+
+            // Calculate inSampleSize
+            options.inSampleSize = calculateInSampleSize(options, reqWidth)
+
+            // Decode bitmap with inSampleSize set
+            options.inJustDecodeBounds = false
+            return BitmapFactory.decodeFile(file.absolutePath, options)
+        }
+
+        /**
+         * Calculate the largest inSampleSize value that is a power of 2 and keeps
+         * width larger than the requested width.
+         *
+         * @param options The Options object, which must have been populated by a previous
+         * decoding call with inJustDecodeBounds=true.
+         * @param reqWidth The target width to fit the image into.
+         */
+        @CheckResult
+        fun calculateInSampleSize(
+            options: BitmapFactory.Options,
+            reqWidth: Int,
+        ): Int {
+            // Raw width of image
+            val width = options.outWidth
+            var inSampleSize = 1
+
+            if (width <= reqWidth) {
+                return 1
+            }
+            val halfWidth = width / 2
+            while ((halfWidth / inSampleSize) >= reqWidth) {
+                inSampleSize *= 2
+            }
+            return inSampleSize
+        }
+    }
+}