Capture: reduce conversions between Mat/Bitmap/ByteArray

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

@@ -109,7 +109,7 @@ class MainViewModel(val imageRepository: ImageRepository, launchMode: LaunchMode
     fun handleImageCaptured(capturedPage: CapturedPage) {
         viewModelScope.launch {
             imageRepository.add(
-                compressJpeg(capturedPage.page, 75),
+                capturedPage.pageJpeg,
                 compressJpeg(capturedPage.source, 90),
                 capturedPage.metadata,
             )

app/src/main/java/org/fairscan/app/domain/CapturedPage.kt

@@ -18,7 +18,7 @@ package org.fairscan.app.domain
 import android.graphics.Bitmap
 
 data class CapturedPage(
-    val page: Bitmap,
+    val pageJpeg: ByteArray,
     val source: Bitmap,
     val metadata: PageMetadata,
 )

app/src/main/java/org/fairscan/app/ui/screens/camera/CameraScreen.kt

@@ -285,7 +285,7 @@ private fun CameraScreenScaffold(
             )
         }
         if (cameraUiState.captureState is CaptureState.CapturePreview) {
-            val page = cameraUiState.captureState.capturedPage.page
+            val page = bitmap(cameraUiState.captureState.capturedPage.pageJpeg)
             CapturedImage(page.asImageBitmap(), thumbnailCoords)
         }
     }
@@ -533,10 +533,10 @@ fun CameraScreenPreviewWithProcessedImage() {
     val p = Point(0 , 0)
     val quad = Quad(p, p, p, p)
     ScreenPreview(CaptureState.CapturePreview(
-        debugImage("uncropped/img01.jpg"),
+        bitmap(debugImage("uncropped/img01.jpg")),
         CapturedPage(
             debugImage("gallica.bnf.fr-bpt6k5530456s-1.jpg"),
-            debugImage("gallica.bnf.fr-bpt6k5530456s-1.jpg"),
+            bitmap(debugImage("gallica.bnf.fr-bpt6k5530456s-1.jpg")),
             PageMetadata(quad, R0, false))))
 }
 
@@ -559,7 +559,7 @@ private fun ScreenPreview(captureState: CaptureState, rotationDegrees: Float = 0
                     contentAlignment = Alignment.TopCenter
                 ) {
                     Image(
-                        debugImage("uncropped/img01.jpg").asImageBitmap(),
+                        bitmap(debugImage("uncropped/img01.jpg")).asImageBitmap(),
                         modifier=Modifier.rotate(rotationDegrees),
                         contentDescription = null
                     )
@@ -591,9 +591,9 @@ private fun ScreenPreview(captureState: CaptureState, rotationDegrees: Float = 0
 }
 
 @Composable
-private fun debugImage(imgName: String): Bitmap {
+private fun debugImage(imgName: String): ByteArray {
     val context = LocalContext.current
-    return context.assets.open(imgName).use { input ->
-        BitmapFactory.decodeStream(input)
-    }
+    return context.assets.open(imgName).readBytes()
 }
+
+private fun bitmap(jpeg: ByteArray): Bitmap = BitmapFactory.decodeByteArray(jpeg, 0, jpeg.size)

app/src/main/java/org/fairscan/app/ui/screens/camera/CameraViewModel.kt

@@ -37,6 +37,7 @@ import org.fairscan.imageprocessing.ImageSize
 import org.fairscan.imageprocessing.Mask
 import org.fairscan.imageprocessing.Quad
 import org.fairscan.imageprocessing.detectDocumentQuad
+import org.fairscan.imageprocessing.encodeJpeg
 import org.fairscan.imageprocessing.extractDocument
 import org.fairscan.imageprocessing.isColoredDocument
 import org.fairscan.imageprocessing.scaledTo
@@ -218,27 +219,14 @@ fun extractDocumentFromBitmap(
     val isColored = isColoredDocument(bgr, mask, quad)
     val maxPixels = ExportQuality.BALANCED.maxPixels
     val page = extractDocument(bgr, quad, rotationDegrees, isColored, maxPixels)
-    val outBgr = page
+    val pageJpeg = encodeJpeg(page, ExportQuality.BALANCED.jpegQuality)
     bgr.release()
-    val outBitmap = toBitmap(outBgr)
-    outBgr.release()
+    page.release()
+
     val normalizedQuad = quad.scaledTo(source.width, source.height, 1, 1)
     val baseRotation = Rotation.fromDegrees(rotationDegrees)
     val metadata = PageMetadata(normalizedQuad, baseRotation, isColored)
-    return CapturedPage(outBitmap, source, metadata)
-}
-
-fun toBitmap(bgr: Mat): Bitmap {
-    require(bgr.type() == CvType.CV_8UC3)
-
-    val rgba = Mat()
-    Imgproc.cvtColor(bgr, rgba, Imgproc.COLOR_BGR2RGBA)
-
-    val bmp = createBitmap(bgr.cols(), bgr.rows(), Bitmap.Config.ARGB_8888)
-    Utils.matToBitmap(rgba, bmp)
-
-    rgba.release()
-    return bmp
+    return CapturedPage(pageJpeg, source, metadata)
 }
 
 fun rotateBitmap(source: Bitmap, angle: Float): Bitmap {