Use thumbnails for the list of pages (#39)

app/src/main/java/org/fairscan/app/ImageRepository.kt

@@ -22,13 +22,22 @@ import org.fairscan.app.data.Page
 import java.io.File
 
 const val SCAN_DIR_NAME = "scanned_pages"
+const val THUMBNAIL_DIR_NAME = "thumbnails"
 
-class ImageRepository(appFilesDir: File, val transformations: ImageTransformations) {
+class ImageRepository(
+    appFilesDir: File,
+    val transformations: ImageTransformations,
+    private val thumbnailSizePx: Int,
+) {
 
     private val scanDir: File = File(appFilesDir, SCAN_DIR_NAME).apply {
         if (!exists()) mkdirs()
     }
 
+    private val thumbnailDir: File = File(appFilesDir, THUMBNAIL_DIR_NAME).apply {
+        if (!exists()) mkdirs()
+    }
+
     private val metadataFile = File(scanDir, "document.json")
 
     private var fileNames: MutableList<String> =
@@ -73,6 +82,7 @@ class ImageRepository(appFilesDir: File, val transformations: ImageTransformatio
         val fileName = "${System.currentTimeMillis()}.jpg"
         val file = File(scanDir, fileName)
         file.writeBytes(bytes)
+        writeThumbnail(file)
         fileNames.add(fileName)
         saveMetadata()
     }
@@ -110,6 +120,23 @@ class ImageRepository(appFilesDir: File, val transformations: ImageTransformatio
         return null
     }
 
+    fun getThumbnail(id: String): ByteArray? {
+        val thumbFile = getThumbnailFile(id)
+        if (!thumbFile.exists()) {
+            val originalFile = File(scanDir, id)
+            if (!originalFile.exists()) return null
+            writeThumbnail(originalFile)
+        }
+        return if (thumbFile.exists()) thumbFile.readBytes() else null
+    }
+
+    private fun writeThumbnail(originalFile: File) {
+        val thumbFile = getThumbnailFile(originalFile.name)
+        transformations.resize(originalFile, thumbFile, thumbnailSizePx)
+    }
+
+    private fun getThumbnailFile(id: String): File = File(thumbnailDir, id)
+
     fun movePage(id: String, newIndex: Int) {
         if (!fileNames.remove(id)) return
         val safeIndex = newIndex.coerceIn(0, fileNames.size)
@@ -118,17 +145,20 @@ class ImageRepository(appFilesDir: File, val transformations: ImageTransformatio
     }
 
     fun delete(id: String) {
-        val file = File(scanDir, id)
+        File(scanDir, id).delete()
-        file.delete()
+        getThumbnailFile(id).delete()
         fileNames.remove(id)
         saveMetadata()
     }
 
     fun clear() {
         fileNames.clear()
+        thumbnailDir.listFiles()?.forEach {
+            file -> file.delete()
+        }
         scanDir.listFiles()?.forEach {
             file -> file.delete()
         }
-        saveMetadata()
+        saveMetadata() // "empty" json file
     }
 }

app/src/main/java/org/fairscan/app/ImageTransformations.kt

@@ -16,8 +16,10 @@ package org.fairscan.app
 
 import java.io.File
 
-fun interface ImageTransformations {
+interface ImageTransformations {
 
     fun rotate(inputFile: File, outputFile: File, clockwise: Boolean)
 
+    fun resize(inputFile: File, outputFile: File, maxSize: Int)
+
 }

app/src/main/java/org/fairscan/app/MainViewModel.kt

@@ -46,6 +46,8 @@ import org.fairscan.app.view.DocumentUiModel
 import java.io.ByteArrayOutputStream
 import java.io.File
 
+const val THUMBNAIL_SIZE_DP = 120
+
 class MainViewModel(
     private val imageSegmentationService: ImageSegmentationService,
     private val imageRepository: ImageRepository,
@@ -57,9 +59,11 @@ class MainViewModel(
         fun getFactory(context: Context) = object : ViewModelProvider.Factory {
             @Suppress("UNCHECKED_CAST")
             override fun <T : ViewModel> create(modelClass: Class<T>, extras: CreationExtras): T {
+                val density = context.resources.displayMetrics.density
+                val thumbnailSizePx = (THUMBNAIL_SIZE_DP * density).toInt()
                 return MainViewModel(
                     ImageSegmentationService(context),
-                    ImageRepository(context.filesDir, OpenCvTransformations()),
+                    ImageRepository(context.filesDir, OpenCvTransformations(), thumbnailSizePx),
                     PdfFileManager(
                         File(context.cacheDir, "pdfs"),
                         Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS),
@@ -83,12 +87,13 @@ class MainViewModel(
         _pageIds.map { ids ->
             DocumentUiModel(
                 pageIds = ids,
-                imageLoader = ::getBitmap
+                imageLoader = ::getBitmap,
+                thumbnailLoader = ::getThumbnail,
             )
         }.stateIn(
             scope = viewModelScope,
             started = SharingStarted.Eagerly,
-            initialValue = DocumentUiModel(persistentListOf(), ::getBitmap)
+            initialValue = DocumentUiModel(persistentListOf(), ::getBitmap, ::getThumbnail)
         )
 
     private val _captureState = MutableStateFlow<CaptureState>(CaptureState.Idle)
@@ -255,6 +260,11 @@ class MainViewModel(
         return bytes?.let { BitmapFactory.decodeByteArray(it, 0, it.size) }
     }
 
+    fun getThumbnail(id: String): Bitmap? {
+        val bytes = imageRepository.getThumbnail(id)
+        return bytes?.let { BitmapFactory.decodeByteArray(it, 0, it.size) }
+    }
+
     private suspend fun generatePdf(): GeneratedPdf = withContext(Dispatchers.IO) {
         val imageIds = imageRepository.imageIds()
         val jpegs = imageIds.asSequence()

app/src/main/java/org/fairscan/app/OpenCvImageTransformations.kt

@@ -14,10 +14,14 @@
  */
 package org.fairscan.app
 
+import android.graphics.Bitmap
+import android.graphics.BitmapFactory
 import org.opencv.core.Core
 import org.opencv.core.Mat
 import org.opencv.imgcodecs.Imgcodecs
 import java.io.File
+import kotlin.math.min
+import androidx.core.graphics.scale
 
 class OpenCvTransformations : ImageTransformations {
     override fun rotate(inputFile: File, outputFile: File, clockwise: Boolean) {
@@ -37,4 +41,15 @@ class OpenCvTransformations : ImageTransformations {
         src.release()
         dst.release()
     }
+
+    override fun resize(inputFile: File, outputFile: File, maxSize: Int) {
+        val bitmap = BitmapFactory.decodeFile(inputFile.absolutePath)
+        val ratio = min(maxSize.toFloat() / bitmap.width, maxSize.toFloat() / bitmap.height)
+        val newW = (bitmap.width * ratio).toInt()
+        val newH = (bitmap.height * ratio).toInt()
+        val scaled = bitmap.scale(newW, newH)
+        outputFile.outputStream().use {
+            scaled.compress(Bitmap.CompressFormat.JPEG, 85, it)
+        }
+    }
 }

app/src/main/java/org/fairscan/app/view/DocumentUiModel.kt

@@ -19,7 +19,8 @@ import kotlinx.collections.immutable.ImmutableList
 
 data class DocumentUiModel(
     val pageIds: ImmutableList<String>,
-    private val imageLoader: (String) -> Bitmap?
+    private val imageLoader: (String) -> Bitmap?,
+    private val thumbnailLoader: (String) -> Bitmap?
 ) {
     fun pageCount(): Int {
         return pageIds.size
@@ -36,4 +37,7 @@ data class DocumentUiModel(
     fun load(index: Int): Bitmap? {
         return imageLoader(pageIds[index])
     }
-}
+    fun loadThumbnail(index: Int): Bitmap? {
+        return thumbnailLoader(pageIds[index])
+    }
+}

app/src/main/java/org/fairscan/app/view/PageList.kt

@@ -49,10 +49,11 @@ import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.unit.Density
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
+import org.fairscan.app.THUMBNAIL_SIZE_DP
 import sh.calvin.reorderable.ReorderableItem
 import sh.calvin.reorderable.rememberReorderableLazyListState
 
-const val PAGE_LIST_ELEMENT_SIZE_DP = 120
+const val PAGE_LIST_ELEMENT_SIZE_DP = THUMBNAIL_SIZE_DP
 
 data class CommonPageListState(
     val document: DocumentUiModel,
@@ -76,8 +77,7 @@ fun CommonPageList(
     val content: LazyListScope.() -> Unit = {
         itemsIndexed(state.document.pageIds, key = { _, item -> item}) { index, item ->
             ReorderableItem(reorderableLazyListState, key = item) { _ ->
-                // TODO Use small images rather than big ones
+                val image = state.document.loadThumbnail(index)
-                val image = state.document.load(index)
                 if (image != null) {
                     PageThumbnail(image, index, state, Modifier.draggableHandle())
                 }
@@ -103,7 +103,7 @@ fun CommonPageList(
     if (state.document.isEmpty()) {
         Box(
             modifier = Modifier
-                .height(120.dp)
+                .height(THUMBNAIL_SIZE_DP.dp)
                 .addPositionCallback(state.onLastItemPosition, LocalDensity.current, 0.5f)
         ) {}
     }

app/src/main/java/org/fairscan/app/view/PreviewUtils.kt

@@ -25,13 +25,14 @@ fun dummyNavigation(): Navigation {
 }
 
 fun fakeDocument(): DocumentUiModel {
-    return DocumentUiModel(persistentListOf()) { _ -> null }
+    return DocumentUiModel(persistentListOf(), { _ -> null }, { _ -> null })
 }
 
 fun fakeDocument(pageIds: ImmutableList<String>, context: Context): DocumentUiModel {
-    return DocumentUiModel(pageIds) { id ->
+    val loader = { id:String ->
         context.assets.open(id).use { input ->
             BitmapFactory.decodeStream(input)
         }
     }
+    return DocumentUiModel(pageIds, loader, loader)
 }

app/src/test/java/org/fairscan/app/ImageRepositoryTest.kt

@@ -35,7 +35,15 @@ class ImageRepositoryTest {
     }
 
     fun repo(): ImageRepository {
-        return ImageRepository(getFilesDir(), {f1,f2,_->f1.copyTo(f2)})
+        val transformations = object : ImageTransformations {
+            override fun rotate(inputFile: File, outputFile: File, clockwise: Boolean) {
+                inputFile.copyTo(outputFile)
+            }
+            override fun resize(inputFile: File, outputFile: File, maxSize: Int) {
+                outputFile.writeBytes(byteArrayOf(inputFile.readBytes()[0]))
+            }
+        }
+        return ImageRepository(getFilesDir(), transformations, 200)
     }
 
     @Test
@@ -46,6 +54,7 @@ class ImageRepositoryTest {
         repo.add(bytes)
         assertThat(repo.imageIds()).hasSize(1)
         assertThat(repo.getContent(repo.imageIds()[0])).isEqualTo(bytes)
+        assertThat(repo.getThumbnail(repo.imageIds()[0])).isEqualTo(byteArrayOf(101))
     }
 
     @Test
@@ -60,6 +69,13 @@ class ImageRepositoryTest {
         assertThat(repo2.imageIds()).isEmpty()
     }
 
+    @Test
+    fun delete_unknown_id() {
+        val repo = repo()
+        repo.delete("x")
+        assertThat(repo.imageIds()).isEmpty()
+    }
+
     @Test
     fun `should find existing files at initialization with no json`() {
         val scanDir = File(getFilesDir(), SCAN_DIR_NAME)
@@ -93,6 +109,12 @@ class ImageRepositoryTest {
         assertThat(repo1.imageIds()).isNotEmpty()
         repo1.clear()
         assertThat(repo1.imageIds()).isEmpty()
+        assertThat(File(getFilesDir(), SCAN_DIR_NAME)
+            .listFiles { f -> f.name.endsWith(".jpg") })
+            .isEmpty()
+        assertThat(File(getFilesDir(), THUMBNAIL_DIR_NAME)
+            .listFiles { f -> f.name.endsWith(".jpg") })
+            .isEmpty()
         val repo2 = repo()
         assertThat(repo2.imageIds()).isEmpty()
     }
@@ -129,6 +151,7 @@ class ImageRepositoryTest {
     fun movePage() {
         val repo = repo()
         repo.add(byteArrayOf(101))
+        Thread.sleep(1L) // to avoid file name clashes
         repo.add(byteArrayOf(110))
         val id0 = repo.imageIds().first()
         val id1 = repo.imageIds().last()