improved image views

composeApp/src/commonMain/kotlin/net/sergeych/toread/ImageViewer.kt

@@ -6,8 +6,11 @@ import androidx.compose.foundation.gestures.detectDragGestures
 import androidx.compose.foundation.gestures.rememberTransformableState
 import androidx.compose.foundation.gestures.transformable
 import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.BoxWithConstraints
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.WindowInsets
+import androidx.compose.foundation.layout.aspectRatio
+import androidx.compose.foundation.layout.fillMaxHeight
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
@@ -35,7 +38,6 @@ import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.geometry.Offset
-import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.graphicsLayer
 import androidx.compose.ui.focus.FocusRequester
 import androidx.compose.ui.focus.focusRequester
@@ -66,6 +68,8 @@ internal fun ImageViewer(
     val focusRequester = remember { FocusRequester() }
     val snackbarHostState = remember { SnackbarHostState() }
     val scope = rememberCoroutineScope()
+    val imageBackgroundColor = readerImageBackgroundColor()
+    val imageAspectRatio = image.bitmap.width.toFloat() / image.bitmap.height.toFloat()
 
     fun setScale(next: Float) {
         scale = next.coerceIn(MinImageScale, MaxImageScale)
@@ -133,11 +137,11 @@ internal fun ImageViewer(
             }
         },
     ) { padding ->
-        Box(
+        BoxWithConstraints(
             modifier = Modifier
                 .fillMaxSize()
                 .padding(padding)
-                .background(Color.Black)
+                .background(readerBackground())
                 .focusRequester(focusRequester)
                 .onPreviewKeyEvent { event ->
                     if (event.type != KeyEventType.KeyDown) return@onPreviewKeyEvent false
@@ -171,19 +175,28 @@ internal fun ImageViewer(
                 },
             contentAlignment = Alignment.Center,
         ) {
-            Image(
-                bitmap = image.bitmap,
-                contentDescription = image.title,
-                modifier = Modifier
-                    .fillMaxSize()
+            val imageModifier = if (maxWidth / maxHeight > imageAspectRatio) {
+                Modifier.fillMaxHeight().aspectRatio(imageAspectRatio)
+            } else {
+                Modifier.fillMaxWidth().aspectRatio(imageAspectRatio)
+            }
+            Box(
+                modifier = imageModifier
                     .graphicsLayer {
                         scaleX = scale
                         scaleY = scale
                         translationX = offset.x
                         translationY = offset.y
-                    },
-                contentScale = ContentScale.Fit,
-            )
+                    }
+                    .background(imageBackgroundColor),
+            ) {
+                Image(
+                    bitmap = image.bitmap,
+                    contentDescription = image.title,
+                    modifier = Modifier.fillMaxSize(),
+                    contentScale = ContentScale.Fit,
+                )
+            }
         }
     }
 }

composeApp/src/commonMain/kotlin/net/sergeych/toread/ReaderContent.kt

@@ -9,6 +9,7 @@ import androidx.compose.foundation.gestures.awaitFirstDown
 import androidx.compose.foundation.gestures.waitForUpOrCancellation
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.BoxWithConstraints
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.ExperimentalLayoutApi
 import androidx.compose.foundation.layout.FlowRow
@@ -16,6 +17,7 @@ import androidx.compose.foundation.layout.PaddingValues
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.aspectRatio
+import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
@@ -47,6 +49,7 @@ import androidx.compose.ui.input.pointer.PointerEventPass
 import androidx.compose.ui.input.pointer.PointerType
 import androidx.compose.ui.input.pointer.pointerInput
 import androidx.compose.ui.layout.ContentScale
+import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.input.nestedscroll.NestedScrollConnection
 import androidx.compose.ui.input.nestedscroll.NestedScrollSource
 import androidx.compose.ui.input.nestedscroll.nestedScroll
@@ -368,6 +371,7 @@ internal fun CoverAndTitle(book: Fb2Book, onImageOpen: (ViewedBookImage) -> Unit
             image = book.coverImages.firstOrNull() ?: book.bodyImages.firstOrNull(),
             modifier = Modifier.width(112.dp).aspectRatio(0.68f),
             contentScale = ContentScale.Crop,
+            fitBackgroundToBitmapBounds = false,
             onOpen = onImageOpen,
         )
         Column(verticalArrangement = Arrangement.spacedBy(6.dp), modifier = Modifier.weight(1f)) {
@@ -564,6 +568,7 @@ private fun BookImage(
     image: Fb2ImageRef?,
     modifier: Modifier = Modifier,
     contentScale: ContentScale = ContentScale.Fit,
+    fitBackgroundToBitmapBounds: Boolean = true,
     onOpen: (ViewedBookImage) -> Unit = {},
 ) {
     val binary = remember(book, image) {
@@ -573,10 +578,12 @@ private fun BookImage(
         binary?.let { decodeBookImage(it) }
     }
     val imageTitle = image?.alt?.ifBlank { null } ?: book.title
-    Box(
+    val imageBackgroundColor = readerImageBackgroundColor()
+    val density = LocalDensity.current
+    BoxWithConstraints(
         modifier = modifier
             .clip(RoundedCornerShape(8.dp))
-            .background(MaterialTheme.colorScheme.surfaceVariant)
+            .background(MaterialTheme.colorScheme.surface)
             .then(
                 if (bitmap != null && binary != null) {
                     Modifier.clickable {
@@ -596,12 +603,23 @@ private fun BookImage(
         contentAlignment = Alignment.Center,
     ) {
         if (bitmap != null) {
-            Image(
-                bitmap = bitmap,
-                contentDescription = imageTitle,
-                modifier = Modifier.fillMaxWidth(),
-                contentScale = contentScale,
-            )
+            val imageAspectRatio = bitmap.width.toFloat() / bitmap.height.coerceAtLeast(1).toFloat()
+            val imageModifier = if (fitBackgroundToBitmapBounds) {
+                val bitmapWidth = with(density) { bitmap.width.toDp() }
+                Modifier
+                    .width(if (bitmapWidth < maxWidth) bitmapWidth else maxWidth)
+                    .aspectRatio(imageAspectRatio)
+            } else {
+                Modifier.fillMaxSize()
+            }
+            Box(imageModifier.background(imageBackgroundColor)) {
+                Image(
+                    bitmap = bitmap,
+                    contentDescription = imageTitle,
+                    modifier = Modifier.fillMaxSize(),
+                    contentScale = contentScale,
+                )
+            }
         } else {
             Text(strings.noImage, style = MaterialTheme.typography.labelMedium, color = MaterialTheme.colorScheme.outline)
         }

composeApp/src/commonMain/kotlin/net/sergeych/toread/SharedUi.kt

@@ -22,7 +22,9 @@ import androidx.compose.runtime.Composable
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Brush
+import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.SolidColor
+import androidx.compose.ui.graphics.lerp
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
 import kotlin.math.roundToInt
@@ -107,6 +109,16 @@ internal fun themedTopAppBarColors(): TopAppBarColors =
 @Composable
 internal fun readerBackground(): Brush = SolidColor(MaterialTheme.colorScheme.background)
 
+@Composable
+internal fun readerImageBackgroundColor(): Color {
+    val surface = MaterialTheme.colorScheme.surface
+    return if (surface.isVisuallyDark()) lerp(surface, Color.White, 0.5f) else surface
+}
+
+private fun Color.isVisuallyDark(): Boolean {
+    val luminance = 0.2126f * red + 0.7152f * green + 0.0722f * blue
+    return luminance < 0.5f
+}
 
 internal fun Int.formatCompact(): String =
     if (this >= 10_000) "${(this / 1000.0).roundToInt()}k" else toString()