Refine BitmapPainter

app/src/main/kotlin/com/hippo/ehviewer/ui/reader/BitmapPainter.kt

@@ -3,43 +3,37 @@ package com.hippo.ehviewer.ui.reader
 import android.graphics.Bitmap
 import android.graphics.Matrix
 import android.graphics.Paint
+import android.graphics.RectF
+import androidx.compose.ui.geometry.Size
 import androidx.compose.ui.graphics.drawscope.DrawScope
 import androidx.compose.ui.graphics.drawscope.drawIntoCanvas
 import androidx.compose.ui.graphics.nativeCanvas
 import androidx.compose.ui.graphics.painter.Painter
-import androidx.compose.ui.unit.IntOffset
-import androidx.compose.ui.unit.IntSize
-import androidx.compose.ui.unit.toOffset
-import androidx.compose.ui.unit.toSize
+import androidx.compose.ui.unit.IntRect
+import androidx.compose.ui.util.fastRoundToInt
 
-class BitmapPainter(
-    private val image: Bitmap,
-    srcOffset: IntOffset = IntOffset.Zero,
-    srcSize: IntSize = IntSize(image.width, image.height),
-) : Painter() {
+class BitmapPainter(private val bitmap: Bitmap, srcRect: IntRect) : Painter() {
 
-    private val offset = (-srcOffset).toOffset()
+    private val srcRect = with(srcRect) {
+        RectF(left.toFloat(), top.toFloat(), right.toFloat(), bottom.toFloat())
+    }
 
-    private val srcSize = srcSize.toSize()
+    private val dstRect = RectF()
 
     private val matrix = Matrix()
 
+    // Use the overload that takes a `Matrix` to bypass the 100 MB size limit
     override fun DrawScope.onDraw() = drawIntoCanvas {
-        // Use the overload that takes a `Matrix` to bypass the 100 MB size limit
-        it.nativeCanvas.drawBitmap(
-            image,
-            matrix.apply {
-                setTranslate(offset.x, offset.y)
-                postScale(size.width / srcSize.width, size.height / srcSize.height)
-            },
-            bitmapPaint,
-        )
+        dstRect.right = size.width.fastRoundToInt().toFloat()
+        dstRect.bottom = size.height.fastRoundToInt().toFloat()
+        matrix.setRectToRect(srcRect, dstRect, Matrix.ScaleToFit.FILL)
+        it.nativeCanvas.drawBitmap(bitmap, matrix, paint)
     }
 
-    override val intrinsicSize get() = srcSize
+    override val intrinsicSize get() = Size(srcRect.width(), srcRect.height())
 
     companion object {
-        private val bitmapPaint = Paint().apply {
+        private val paint = Paint().apply {
             isAntiAlias = true
             isFilterBitmap = true
             isDither = true

app/src/main/kotlin/com/hippo/ehviewer/ui/reader/PagerItem.kt

@@ -117,11 +117,7 @@ fun PagerItem(
 }
 
 private fun Image.toPainter() = when (val image = innerImage) {
-    is BitmapImage -> BitmapPainter(
-        image = image.bitmap,
-        srcOffset = rect.topLeft,
-        srcSize = rect.size,
-    )
+    is BitmapImage -> BitmapPainter(image.bitmap, rect)
     is DrawableImage -> DrawablePainter(image.drawable)
     else -> unreachable()
 }