From 3d09f46844757310f856691ece7e533766676f20 Mon Sep 17 00:00:00 2001
From: Kilian Schuettler <kilian.schuettler@knecon.com>
Date: Wed, 15 Nov 2023 15:52:55 +0100
Subject: [PATCH] RED-7669: optimize OCR-module performance * don't despeckle
 small images

---
 .../processor/model/ExtractedOcrImage.java    | 85 ++++++++++++++++++-
 1 file changed, 81 insertions(+), 4 deletions(-)

diff --git a/ocr-service-v1/ocr-service-processor/src/main/java/com/knecon/fforesight/service/ocr/processor/model/ExtractedOcrImage.java b/ocr-service-v1/ocr-service-processor/src/main/java/com/knecon/fforesight/service/ocr/processor/model/ExtractedOcrImage.java
index 6455f97..472287e 100644
--- a/ocr-service-v1/ocr-service-processor/src/main/java/com/knecon/fforesight/service/ocr/processor/model/ExtractedOcrImage.java
+++ b/ocr-service-v1/ocr-service-processor/src/main/java/com/knecon/fforesight/service/ocr/processor/model/ExtractedOcrImage.java
@@ -54,10 +54,87 @@ public class ExtractedOcrImage implements OcrImage {
     @SneakyThrows
     synchronized private Pix binarize(BufferedImage image, float imageDpi, int targetDpi) {
 
-        ImageProcessingUtils.setAlphaChannelToWhite(image);
-        Pix grayScale = ImageProcessingUtils.convertToGrayScale(image);
-        Pix scaledUp = ImageProcessingUtils.scaleToTargetDpi(imageDpi, targetDpi, grayScale);
-        return ImageProcessingUtils.despecklePix(scaledUp);
+        setAlphaChannelToWhite(image);
+        Pix grayScale = convertToGrayScale(image);
+        Pix scaledUp = scaleToTargetDpi(imageDpi, targetDpi, grayScale);
+        return despecklePix(scaledUp);
+    }
+
+
+    private static Pix despecklePix(Pix pix) {
+
+        assert pix.d == 8;
+        Pix despeckled;
+        if (pix.w < 100 || pix.h < 100) {
+            // too small to properly despeckle, just binarize instead.
+            despeckled = Leptonica1.pixThresholdToBinary(pix, 180);
+        } else {
+            despeckled = LeptUtils.despeckle(pix, LeptUtils.SEL_STR3, 3); // sometimes this fails and I can't figure out why. Then we skip the despeckling and just simply convert to binary. Might have something to do with Imagesize, not sure though...
+            if (despeckled == null) {
+                despeckled = Leptonica1.pixThresholdToBinary(pix, 180);
+            }
+        }
+        if (pix != despeckled) {
+            LeptUtils.disposePix(pix);
+        }
+        return despeckled;
+    }
+
+
+    private static Pix scaleToTargetDpi(float imageDpi, int targetDpi, Pix grayScale) {
+
+        float targetFactor = targetDpi / imageDpi;
+
+        if (targetFactor > 3) {
+            Pix scaledUp;
+            scaledUp = Leptonica1.pixScaleGray4xLI(grayScale);
+            LeptUtils.disposePix(grayScale);
+            return scaledUp;
+        } else if (targetFactor > 1.9) {
+            Pix scaledUp;
+            scaledUp = Leptonica1.pixScaleGray2xLI(grayScale);
+            LeptUtils.disposePix(grayScale);
+            return scaledUp;
+        } else {
+            return grayScale;
+        }
+    }
+
+
+    private static Pix convertToGrayScale(BufferedImage image) throws IOException {
+
+        Pix pix = LeptUtils.convertImageToPix(image);
+        if (pix.d == 8) {
+            return pix;
+        } else if (pix.d == 32) {
+            Pix grayScale = Leptonica1.pixConvertRGBToGrayFast(pix);
+            LeptUtils.disposePix(pix);
+            return grayScale;
+        } else {
+            Pix grayScale = Leptonica1.pixConvert1To8(null, pix, (byte) 0, (byte) 255);
+            LeptUtils.disposePix(pix);
+            return grayScale;
+        }
+    }
+
+
+    private static void setAlphaChannelToWhite(BufferedImage image) {
+
+        if (image.getTransparency() == Transparency.TRANSLUCENT) {
+            // NOTE: For BITMASK images, the color model is likely IndexColorModel,
+            // and this model will contain the "real" color of the transparent parts
+            // which is likely a better fit than unconditionally setting it to white.
+
+            // Fill background  with white
+            Graphics2D graphics = image.createGraphics();
+            try {
+                graphics.setComposite(AlphaComposite.DstOver); // Set composite rules to paint "behind"
+                graphics.setPaint(Color.WHITE);
+                graphics.fillRect(0, 0, image.getWidth(), image.getHeight());
+            } finally {
+                graphics.dispose();
+            }
+        }
     }