Improve distinction between color and grayscale documents (#79)

Better differentiate color and grayscale documents:
- Look for colored pixels only in the intersection of the mask and quadrilateral
- Apply a white balance (grey world) to the document
- Exclude pixels with extreme luminance
- Erode segmentation mask

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

@@ -151,9 +151,17 @@ class ImageSegmentationService(private val context: Context, private val logger:
         }
 
         override fun toMat(): Mat {
-            val mat = Mat(height, width, CvType.CV_32FC1)
-            mat.put(0, 0, probmap)
-            return mat
+            val threshold = 0.5f
+
+            val mask = Mat(height, width, CvType.CV_8UC1)
+            val data = ByteArray(width * height)
+
+            for (i in probmap.indices) {
+                data[i] = if (probmap[i] >= threshold) 255.toByte() else 0.toByte()
+            }
+
+            mask.put(0, 0, data)
+            return mask
         }
     }
 

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

@@ -31,12 +31,15 @@ import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
 import org.fairscan.app.AppContainer
+import org.fairscan.imageprocessing.Mask
 import org.fairscan.imageprocessing.Quad
 import org.fairscan.imageprocessing.detectDocumentQuad
 import org.fairscan.imageprocessing.extractDocument
 import org.fairscan.imageprocessing.scaledTo
 import org.opencv.android.Utils
+import org.opencv.core.CvType
 import org.opencv.core.Mat
+import org.opencv.imgproc.Imgproc
 import java.io.ByteArrayOutputStream
 
 sealed interface CameraEvent {
@@ -130,6 +133,7 @@ class CameraViewModel(appContainer: AppContainer): ViewModel() {
         if (segmentation != null) {
             val mask = segmentation.segmentation
             var quad = detectDocumentQuad(mask, isLiveAnalysis = false)
+            val rotationDegrees = imageProxy.imageInfo.rotationDegrees
             if (quad == null) {
                 val now = System.currentTimeMillis()
                 lastSuccessfulLiveAnalysisState?.timestamp?.let {
@@ -139,7 +143,7 @@ class CameraViewModel(appContainer: AppContainer): ViewModel() {
                 val recentLive = lastSuccessfulLiveAnalysisState?.takeIf {
                     now - it.timestamp <= 1500
                 }
-                val rotations = (-imageProxy.imageInfo.rotationDegrees / 90) + 4
+                val rotations = (-rotationDegrees / 90) + 4
                 quad = recentLive?.documentQuad?.rotate90(rotations, mask.width, mask.height)
                 if (quad != null) {
                     Log.i("Quad", "Using quad taken in live analysis; rotations=$rotations")
@@ -147,7 +151,7 @@ class CameraViewModel(appContainer: AppContainer): ViewModel() {
             }
             if (quad != null) {
                 val resizedQuad = quad.scaledTo(mask.width, mask.height, bitmap.width, bitmap.height)
-                corrected = extractDocumentFromBitmap(bitmap, resizedQuad, imageProxy.imageInfo.rotationDegrees)
+                corrected = extractDocumentFromBitmap(bitmap, resizedQuad, rotationDegrees, mask)
             }
         }
         return@withContext corrected
@@ -180,18 +184,33 @@ sealed class CaptureState {
     data class CaptureError(override val frozenImage: Bitmap) : CaptureState()
     data class CapturePreview(
         override val frozenImage: Bitmap,
-        val processed: Bitmap
+        val processed: Bitmap,
     ) : CaptureState()
 }
 
-fun extractDocumentFromBitmap(originalBitmap: Bitmap, quad: Quad, rotationDegrees: Int): Bitmap {
-    val inputMat = Mat()
-    Utils.bitmapToMat(originalBitmap, inputMat)
-    return toBitmap(extractDocument(inputMat, quad, rotationDegrees))
+fun extractDocumentFromBitmap(image: Bitmap, quad: Quad, rotationDegrees: Int, mask: Mask): Bitmap {
+    val rgba = Mat()
+    Utils.bitmapToMat(image, rgba)
+    val bgr = Mat()
+    Imgproc.cvtColor(rgba, bgr, Imgproc.COLOR_RGBA2BGR) // CV_8UC4 → CV_8UC3
+    rgba.release()
+    val outBgr = extractDocument(bgr, quad, rotationDegrees, mask)
+    bgr.release()
+    val outBitmap = toBitmap(outBgr)
+    outBgr.release()
+    return outBitmap
 }
 
-private fun toBitmap(mat: Mat): Bitmap {
-    val outputBitmap = createBitmap(mat.cols(), mat.rows())
-    Utils.matToBitmap(mat, outputBitmap)
-    return outputBitmap
+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
 }
+

evaluation/.gitignore

@@ -1,5 +1,6 @@
 /build
 /dataset/images
 /dataset/masks
+/dataset/metadata
 /python/venv
 /reports

evaluation/src/main/java/org/fairscan/evaluation/ColorDetectionEvaluator.kt

@@ -0,0 +1,152 @@
+/*
+ * Copyright 2025 Pierre-Yves Nicolas
+ *
+ * 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 <https://www.gnu.org/licenses/>.
+ */
+package org.fairscan.evaluation
+
+import org.fairscan.imageprocessing.detectDocumentQuad
+import org.fairscan.imageprocessing.extractDocument
+import org.fairscan.imageprocessing.isColoredDocument
+import org.fairscan.imageprocessing.scaledTo
+import org.opencv.core.Mat
+import org.opencv.imgcodecs.Imgcodecs
+import java.io.File
+
+fun main() {
+    nu.pattern.OpenCV.loadLocally()
+    ColorDetectionEvaluator.run()
+}
+
+object ColorDetectionEvaluator {
+
+    fun run() {
+        val root = File("evaluation")
+        val datasetDir = File(root, "dataset")
+        val metadataDir = File(datasetDir, "metadata")
+        val outputDir = File("evaluation/reports/color_detection").apply { mkdirs() }
+
+        val imageMetas = CsvMetadata.readImagesCsv(File(metadataDir, "images.csv"))
+        val documentMetas = CsvMetadata.readDocumentsCsv(File(metadataDir, "documents.csv"))
+
+        val results = mutableListOf<ColorResult>()
+        var nbProcessedImages = 0
+
+        for (meta in imageMetas) {
+            val expected = documentMetas[meta.docId]?.isColored ?: continue
+            val imgName = meta.imgName.removeSuffix(".jpg")
+            val imgFile = File(datasetDir, "images/$imgName.jpg")
+            val maskFile = File(datasetDir, "masks/$imgName.png")
+            if (!imgFile.exists() || !maskFile.exists()) continue
+
+            val mat = Imgcodecs.imread(imgFile.absolutePath)
+            if (mat.empty()) continue
+
+            val maskMat = Imgcodecs.imread(maskFile.absolutePath, Imgcodecs.IMREAD_UNCHANGED)
+            if (maskMat.empty()) continue
+
+            println("Processing ${imgName}...")
+
+            val mask = MatMask(maskMat)
+
+            val quad = detectDocumentQuad(mask, isLiveAnalysis = false)
+                ?.scaledTo(mask.width, mask.height, mat.width(), mat.height())
+
+            val document: Mat = if (quad != null) {
+                extractDocument(mat, quad, 0, mask)
+            } else continue
+
+            val detected = isColoredDocument(mat, mask, quad)
+
+            nbProcessedImages++
+
+            val inputOut = File(outputDir, "${imgName}_input.jpg")
+            Imgcodecs.imwrite(inputOut.absolutePath, mat)
+
+            val outputOut = File(outputDir, "${imgName}_output.jpg")
+            Imgcodecs.imwrite(outputOut.absolutePath, document)
+
+            results += ColorResult(
+                imgName,
+                originalFile = inputOut,
+                documentFile = outputOut,
+                colorCase = ColorCase(expected, detected),
+            )
+        }
+
+        ColorDetectionReport.writeHtml(
+            File(outputDir, "index.html"),
+            Score(results.groupingBy { it.colorCase }.eachCount()),
+            results
+        )
+    }
+}
+
+data class ColorCase(
+    val expected: Boolean,
+    val detected: Boolean
+) {
+    val isMismatch: Boolean get() = expected != detected
+}
+
+data class ColorResult(
+    val imgName: String,
+    val originalFile: File,
+    val documentFile: File,
+    val colorCase: ColorCase
+)
+
+data class Score(
+    val byCase: Map<ColorCase, Int>
+) {
+    val total: Int get() = byCase.values.sum()
+    val mismatchCount: Int get() = byCase.filter { it.key.isMismatch }.values.sum()
+    val accuracy: Double get() = 1.0 - mismatchCount.toDouble() / total
+}
+
+object ColorDetectionReport {
+
+    fun writeHtml(output: File, score: Score, results: List<ColorResult>) {
+        val sb = StringBuilder()
+
+        sb.append("<html><body>")
+        sb.append("<h1>Color Detection Evaluation</h1>")
+        sb.append("<p>Total: ${score.total}</p>")
+        sb.append("<p>Mismatches: ${score.mismatchCount}</p>")
+        sb.append("<p>Accuracy: ${"%.2f".format(score.accuracy * 100)}%</p>")
+
+        score.byCase.forEach { (case, count) ->
+            sb.append("<p>expectedColor=${case.expected} / detectedColor=${case.detected} : $count</p>")
+        }
+
+        for (c in listOf(ColorCase(true, false), ColorCase(false, true))) {
+            sb.append("<h2>expectedColor=${c.expected}  / detectedColor=${c.detected}</h2>")
+            for (r in results.filter { it.colorCase == c }) {
+                sb.append(
+                    """
+                <div style="margin-bottom:20px;">
+                    <div style="display:flex; gap:20px;">
+                        <div><img width="300" src="${r.originalFile.name}" /></div>
+                        <div><img width="300" src="${r.documentFile.name}" /></div>
+                    </div>
+                </div>
+            """.trimIndent()
+                )
+            }
+        }
+
+        sb.append("</body></html>")
+        output.writeText(sb.toString())
+    }
+}
+
+

evaluation/src/main/java/org/fairscan/evaluation/CsvMetadata.kt

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2025 Pierre-Yves Nicolas
+ *
+ * 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 <https://www.gnu.org/licenses/>.
+ */
+package org.fairscan.evaluation
+
+import java.io.File
+
+data class ImageMeta(
+    val imgName: String,
+    val docId: String
+)
+
+data class DocumentMeta(
+    val docId: String,
+    val isColored: Boolean
+)
+
+object CsvMetadata {
+
+    fun readImagesCsv(file: File): List<ImageMeta> {
+        return file.readLines()
+            .drop(1) // skip header
+            .map { line ->
+                val cols = line.split(',')
+                ImageMeta(
+                    imgName = cols[0].trim(),
+                    docId = cols[1].trim()
+                )
+            }
+    }
+
+    fun readDocumentsCsv(file: File): Map<String, DocumentMeta> {
+        return file.readLines()
+            .drop(1)
+            .map { line ->
+                val cols = line.split(',')
+                val docId = cols[0].trim()
+                val isColored = cols[1].trim().equals("TRUE", ignoreCase = true)
+                DocumentMeta(docId, isColored)
+            }
+            .associateBy { it.docId }
+    }
+}

evaluation/src/main/java/org/fairscan/evaluation/DatasetEvaluator.kt

@@ -31,7 +31,7 @@ class MatMask(private val mat: Mat) : Mask {
     override val width: Int get() = mat.width()
     override val height: Int get() = mat.height()
 
-    override fun toMat(): Mat = mat
+    override fun toMat(): Mat = mat.clone()
 }
 
 object DatasetEvaluator {
@@ -71,7 +71,7 @@ object DatasetEvaluator {
                 ?.scaledTo(mask.width, mask.height, inputMat.width(), inputMat.height())
 
             val corrected: Mat? = if (quad != null) {
-                extractDocument(inputMat, quad = quad, rotationDegrees = 0)
+                extractDocument(inputMat, quad = quad, rotationDegrees = 0, mask)
             } else null
 
             val inputOut = File(outputDir, "${e.name}_input.jpg")

imageprocessing/src/main/java/org/fairscan/imageprocessing/ColorDetection.kt

@@ -0,0 +1,236 @@
+/*
+ * Copyright 2025 Pierre-Yves Nicolas
+ *
+ * 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 <https://www.gnu.org/licenses/>.
+ */
+package org.fairscan.imageprocessing
+
+import org.opencv.core.Core
+import org.opencv.core.CvType
+import org.opencv.core.CvType.CV_8UC1
+import org.opencv.core.Mat
+import org.opencv.core.Mat.zeros
+import org.opencv.core.MatOfPoint
+import org.opencv.core.Scalar
+import org.opencv.core.Size
+import org.opencv.imgproc.Imgproc
+import org.opencv.imgproc.Imgproc.fillConvexPoly
+import kotlin.math.roundToInt
+import kotlin.math.sqrt
+
+fun isColoredDocument(
+    img: Mat,
+    mask: Mask,
+    quad: Quad,
+    chromaThreshold: Double = 17.5,
+    proportionThreshold: Double = 0.0003,
+    luminanceMin: Double = 40.0,
+    luminanceMax: Double = 180.0
+): Boolean {
+
+    // Work on a reasonable size (for correct performance)
+    val resizedImg = resizeForMaxPixels(img, 1024.0 * 768.0)
+    val workSize = resizedImg.size()
+
+    // 1) Compute doc mask (mask ∩ quad)
+    val docMask = documentMask(mask, quad, img.size(), workSize)
+
+    // 2) Apply white balance only inside document
+    val whiteBalanced = applyGrayWorldToDocument(resizedImg, docMask)
+
+    // 3) Convert to Lab, see https://en.wikipedia.org/wiki/CIELAB_color_space
+    val lab = Mat()
+    Imgproc.cvtColor(whiteBalanced, lab, Imgproc.COLOR_BGR2Lab)
+
+    // 4) Split Lab
+    val channels = ArrayList<Mat>()
+    Core.split(lab, channels)
+    val luminance = channels[0]
+    val a = channels[1]
+    val b = channels[2]
+
+    // 5) Compute chroma
+    val chroma = chroma(a, b)
+
+    val colorMask = Mat()
+    Imgproc.threshold(chroma, colorMask, chromaThreshold, 255.0, Imgproc.THRESH_BINARY)
+    colorMask.convertTo(colorMask, CvType.CV_8U)
+
+    // 6) Create luminance mask L ∈ [luminanceMin, luminanceMax]
+    val luminanceMask = Mat()
+    Core.inRange(luminance, Scalar(luminanceMin), Scalar(luminanceMax), luminanceMask)
+
+    // 7) Combine colorMask & luminanceMask & docMask
+    val tmp = Mat()
+    Core.bitwise_and(colorMask, luminanceMask, tmp)
+
+    val restrictedMask = Mat()
+    Core.bitwise_and(tmp, docMask, restrictedMask)
+
+    val coloredPixels = Core.countNonZero(restrictedMask)
+    val totalPixels = Core.countNonZero(docMask)
+
+    // 8) Cleanup
+    resizedImg.release()
+    whiteBalanced.release()
+    lab.release()
+    channels.forEach { it.release() }
+    chroma.release()
+    colorMask.release()
+    luminanceMask.release()
+    tmp.release()
+    restrictedMask.release()
+    docMask.release()
+
+    if (totalPixels == 0) return false
+
+    val proportion = coloredPixels.toDouble() / totalPixels.toDouble()
+    return proportion > proportionThreshold
+}
+
+private fun resizeForMaxPixels(img: Mat, maxPixels: Double): Mat {
+    val origPixels = img.width() * img.height()
+    if (origPixels <= maxPixels) {
+        return img.clone()
+    }
+    val scale = sqrt(maxPixels / origPixels)
+    val size = Size(img.width() * scale, img.height() * scale)
+    val resizedImg = Mat()
+    Imgproc.resize(img, resizedImg, size, 0.0, 0.0, Imgproc.INTER_AREA)
+    return resizedImg
+}
+
+private fun chroma(a: Mat, b: Mat): Mat {
+    val aFloat = Mat()
+    val bFloat = Mat()
+    a.convertTo(aFloat, CvType.CV_32F)
+    b.convertTo(bFloat, CvType.CV_32F)
+
+    val aShifted = Mat()
+    val bShifted = Mat()
+    Core.subtract(aFloat, Scalar(128.0), aShifted)
+    Core.subtract(bFloat, Scalar(128.0), bShifted)
+
+    val chroma = Mat()
+    Core.magnitude(aShifted, bShifted, chroma)
+
+    aFloat.release()
+    bFloat.release()
+    aShifted.release()
+    bShifted.release()
+
+    return chroma
+}
+
+private fun erodeBorder(mask: Mat, quad: Quad): Mat {
+    val minDim = quad.edges().minOf { it.norm() }
+    var k = (minDim * 0.02).roundToInt()
+    k = k.coerceIn(3, 15)
+    if (k % 2 == 0) k += 1
+
+    val kernel = Imgproc.getStructuringElement(
+        Imgproc.MORPH_ELLIPSE,
+        Size(k.toDouble(), k.toDouble())
+    )
+    val erodedMask = Mat()
+    Imgproc.morphologyEx(mask, erodedMask, Imgproc.MORPH_ERODE, kernel)
+    kernel.release()
+    return erodedMask
+}
+
+private fun documentMask(
+    mask: Mask,
+    quad: Quad,
+    origSize: Size,
+    workSize: Size,
+): Mat {
+    val resizedMask = Mat()
+    val maskMat = mask.toMat()
+    Imgproc.resize(maskMat, resizedMask, workSize, 0.0, 0.0, Imgproc.INTER_AREA)
+    val resizedQuad = quad.scaledTo(
+        origSize.width, origSize.height, workSize.width, workSize.height
+    )
+    val erodedMask = erodeBorder(resizedMask, resizedQuad)
+    val quadMask = zeros(erodedMask.size(), CV_8UC1)
+    val pts = MatOfPoint(
+        resizedQuad.topLeft.toCv(), resizedQuad.topRight.toCv(), resizedQuad.bottomRight.toCv(), resizedQuad.bottomLeft.toCv())
+    fillConvexPoly(quadMask, pts, Scalar(255.0))
+
+    val docMask = Mat()
+    Core.bitwise_and(erodedMask, quadMask, docMask)
+
+    quadMask.release()
+    pts.release()
+    erodedMask.release()
+    resizedMask.release()
+    maskMat.release()
+
+    return docMask
+}
+
+fun applyGrayWorldToDocument(
+    img: Mat,
+    docMask: Mat,
+): Mat {
+    require(img.type() == CvType.CV_8UC3)
+
+    val nonZero = Core.countNonZero(docMask)
+    if (nonZero == 0) {
+        docMask.release()
+        return img.clone()
+    }
+
+    // compute mean per channel on docMask (B,G,R)
+    val meanScalar = Core.mean(img, docMask) // Scalar(bMean, gMean, rMean, alpha)
+    val meanB = meanScalar.`val`[0]
+    val meanG = meanScalar.`val`[1]
+    val meanR = meanScalar.`val`[2]
+
+    // safety: avoid division by very small values
+    val eps = 1e-6
+    val meanBsafe = if (meanB < eps) eps else meanB
+    val meanGsafe = if (meanG < eps) eps else meanG
+    val meanRsafe = if (meanR < eps) eps else meanR
+
+    val meanGray = (meanBsafe + meanGsafe + meanRsafe) / 3.0
+
+    val scaleB = meanGray / meanBsafe
+    val scaleG = meanGray / meanGsafe
+    val scaleR = meanGray / meanRsafe
+
+    // apply per-channel scaling only on docMask
+    // convert to float
+    val imgF = Mat()
+    img.convertTo(imgF, CvType.CV_32FC3)
+
+    // build scales scalar in BGR order
+    val scales = Scalar(scaleB, scaleG, scaleR)
+
+    // prepare scaled full image (float)
+    val scaledF = Mat()
+    Core.multiply(imgF, scales, scaledF)
+
+    // convert scaledF back to 8U
+    val scaled8 = Mat()
+    scaledF.convertTo(scaled8, CvType.CV_8UC3)
+
+    // result = original copy, then copy scaled pixels where docMask != 0
+    val result = img.clone()
+    scaled8.copyTo(result, docMask)
+
+    // cleanup
+    imgF.release()
+    scaledF.release()
+    scaled8.release()
+
+    return result
+}

imageprocessing/src/main/java/org/fairscan/imageprocessing/DocumentDetection.kt

@@ -18,7 +18,6 @@ import org.fairscan.imageprocessing.quad.detectDocumentQuadFromProbmap
 import org.fairscan.imageprocessing.quad.findQuadFromRightAngles
 import org.fairscan.imageprocessing.quad.minAreaRect
 import org.opencv.core.Core
-import org.opencv.core.CvType
 import org.opencv.core.Mat
 import org.opencv.core.MatOfPoint
 import org.opencv.core.MatOfPoint2f
@@ -62,10 +61,7 @@ fun detectDocumentQuad(mask: Mask, isLiveAnalysis: Boolean, minQuadAreaRatio: Do
 }
 
 private fun biggestContour(mat: Mat): Pair<MatOfPoint2f?, Double> {
-    val mat8u = Mat()
-    mat.convertTo(mat8u, CvType.CV_8UC1, 255.0)
-
-    val refinedMask = refineMask(mat8u)
+    val refinedMask = refineMask(mat)
 
     val blurred = Mat()
     Imgproc.GaussianBlur(refinedMask, blurred, Size(5.0, 5.0), 0.0)
@@ -116,7 +112,12 @@ fun refineMask(original: Mat): Mat {
     return opened
 }
 
-fun extractDocument(inputMat: Mat, quad: Quad, rotationDegrees: Int): Mat {
+fun extractDocument(
+    inputMat: Mat,
+    quad: Quad,
+    rotationDegrees: Int,
+    mask: Mask,
+): Mat {
     val widthTop = norm(quad.topLeft, quad.topRight)
     val widthBottom = norm(quad.bottomLeft, quad.bottomRight)
     val targetWidth = (widthTop + widthBottom) / 2
@@ -144,7 +145,8 @@ fun extractDocument(inputMat: Mat, quad: Quad, rotationDegrees: Int): Mat {
     Imgproc.warpPerspective(inputMat, outputMat, transform, outputSize)
 
     val resized = resize(outputMat, 1500.0)
-    val enhanced = enhanceCapturedImage(resized)
+    val isColored = isColoredDocument(inputMat, mask, quad)
+    val enhanced = enhanceCapturedImage(resized, isColored)
     val rotated = rotate(enhanced, rotationDegrees)
 
     return rotated

imageprocessing/src/main/java/org/fairscan/imageprocessing/Geometry.kt

@@ -81,9 +81,9 @@ fun createQuad(vertices: List<Point>): Quad {
     return Quad(sorted[0], sorted[1], sorted[2], sorted[3])
 }
 
-fun Quad.scaledTo(fromWidth: Int, fromHeight: Int, toWidth: Int, toHeight: Int): Quad {
-    val scaleX = toWidth.toFloat() / fromWidth
-    val scaleY = toHeight.toFloat() / fromHeight
+fun Quad.scaledTo(fromWidth: Double, fromHeight: Double, toWidth: Double, toHeight: Double): Quad {
+    val scaleX = toWidth / fromWidth
+    val scaleY = toHeight / fromHeight
     return Quad(
         topLeft = topLeft.scaled(scaleX, scaleY),
         topRight = topRight.scaled(scaleX, scaleY),
@@ -92,6 +92,14 @@ fun Quad.scaledTo(fromWidth: Int, fromHeight: Int, toWidth: Int, toHeight: Int):
     )
 }
 
-fun Point.scaled(scaleX: Float, scaleY: Float): Point {
+fun Quad.scaledTo(fromWidth: Int, fromHeight: Int, toWidth: Int, toHeight: Int): Quad {
+    return scaledTo(
+        fromWidth.toDouble(),
+        fromHeight.toDouble(),
+        toWidth.toDouble(),
+        toHeight.toDouble())
+}
+
+fun Point.scaled(scaleX: Double, scaleY: Double): Point {
     return Point((x * scaleX), (y * scaleY))
 }

imageprocessing/src/main/java/org/fairscan/imageprocessing/PostProcessing.kt

@@ -22,8 +22,8 @@ import org.opencv.core.Size
 import org.opencv.imgproc.Imgproc
 import kotlin.math.max
 
-fun enhanceCapturedImage(img: Mat): Mat {
-    return if (isColoredDocument(img)) {
+fun enhanceCapturedImage(img: Mat, isColored: Boolean): Mat {
+    return if (isColored) {
         val result = Mat()
         Core.convertScaleAbs(img, result, 1.2, 10.0)
         result
@@ -36,63 +36,6 @@ fun enhanceCapturedImage(img: Mat): Mat {
     }
 }
 
-fun isColoredDocument(
-    img: Mat,
-    chromaThreshold: Double = 20.0,
-    proportionThreshold: Double = 0.001
-): Boolean {
-    val lab = Mat()
-    Imgproc.cvtColor(img, lab, Imgproc.COLOR_BGR2Lab)
-
-    val channels = ArrayList<Mat>()
-    Core.split(lab, channels)
-    val a = channels[1]
-    val b = channels[2]
-
-    val aFloat = Mat()
-    val bFloat = Mat()
-    a.convertTo(aFloat, CvType.CV_32F)
-    b.convertTo(bFloat, CvType.CV_32F)
-
-    val aShifted = Mat()
-    val bShifted = Mat()
-    Core.subtract(aFloat, Scalar(128.0), aShifted)
-    Core.subtract(bFloat, Scalar(128.0), bShifted)
-
-    val aSq = Mat()
-    val bSq = Mat()
-    Core.multiply(aShifted, aShifted, aSq)
-    Core.multiply(bShifted, bShifted, bSq)
-
-    val sumSq = Mat()
-    Core.add(aSq, bSq, sumSq)
-
-    val chroma = Mat()
-    Core.sqrt(sumSq, chroma)
-
-    val mask = Mat()
-    Imgproc.threshold(chroma, mask, chromaThreshold, 1.0, Imgproc.THRESH_BINARY)
-    val coloredPixels = Core.countNonZero(mask)
-
-    val totalPixels = chroma.rows() * chroma.cols()
-    val proportion = coloredPixels.toDouble() / totalPixels.toDouble()
-
-    lab.release()
-    channels.forEach { it.release() }
-    aFloat.release()
-    bFloat.release()
-    aShifted.release()
-    bShifted.release()
-    aSq.release()
-    bSq.release()
-    sumSq.release()
-    chroma.release()
-    mask.release()
-
-    return proportion > proportionThreshold
-}
-
-
 private fun multiScaleRetinex(img: Mat): Mat {
     val imageSize = img.size()
     val maxDim = max(imageSize.width, imageSize.height)