Add inpaint to fill black areas after warping.

It uses SHIFTMAP algorithm.
NOTE: it can be slow !

Author: Dan Oprea

app/src/main/java/com/dan/perspective/MainActivity.kt

@@ -33,9 +33,11 @@ import org.opencv.core.Core.minMaxLoc
 import org.opencv.core.CvType.*
 import org.opencv.core.Mat
 import org.opencv.core.MatOfInt
+import org.opencv.core.Scalar
 import org.opencv.core.Size
 import org.opencv.imgcodecs.Imgcodecs
 import org.opencv.imgproc.Imgproc.*
+import org.opencv.xphoto.Xphoto
 import java.io.File
 import kotlin.math.PI
 import kotlin.math.abs
@@ -240,7 +242,7 @@ class MainActivity : AppCompatActivity() {
                     )
                 )
 
-                return true;
+                return true
             }
         }
 
@@ -395,6 +397,7 @@ class MainActivity : AppCompatActivity() {
         binding.radioButtonPointDirectionAll.isEnabled = enabled
         binding.radioButtonPointDirectionHorizontal.isEnabled = enabled
         binding.radioButtonPointDirectionVertical.isEnabled = enabled
+        binding.checkBoxInpaint.isEnabled = enabled
 
         menuSave?.isEnabled = enabled
         menuPrevPerspective?.isEnabled = enabled && settings.prevHeight > 0
@@ -420,7 +423,7 @@ class MainActivity : AppCompatActivity() {
     private fun saveImageAsync() {
         if (inputImage.empty()) return
 
-        warpImageAsync()
+        warpImageAsync( binding.checkBoxInpaint.isChecked )
         if (outputImage.empty()) return
 
         setBusyDialogTitleAsync(MSG_SAVE)
@@ -523,7 +526,7 @@ class MainActivity : AppCompatActivity() {
         }
     }
 
-    private fun warpImageAsync() {
+    private fun warpImageAsync( inpaint: Boolean ) {
         if (inputImage.empty()) return
         if (!outputImage.empty()) return
 
@@ -557,6 +560,14 @@ class MainActivity : AppCompatActivity() {
         val perspectiveMat = getPerspectiveTransform(srcMat, destMat)
         warpPerspective(inputImage, outputImage, perspectiveMat, inputImage.size(), INTER_LANCZOS4)
 
+        if (inpaint) {
+            val tmpMat = Mat(inputImage.width(), inputImage.height(), CV_8UC1, Scalar(255.0))
+            val warpedMask = Mat()
+            warpPerspective(tmpMat, warpedMask, perspectiveMat, inputImage.size(), INTER_NEAREST)
+            Xphoto.inpaint( outputImage, warpedMask, tmpMat, Xphoto.INPAINT_SHIFTMAP )
+            outputImage = tmpMat
+        }
+
         runOnUiThread {
             binding.imagePreview.setBitmap(matToBitmap(outputImage))
         }
@@ -566,8 +577,10 @@ class MainActivity : AppCompatActivity() {
         if (inputImage.empty()) return
         if (!outputImage.empty()) return
 
+        val inpaint = binding.checkBoxInpaint.isChecked
+
         runAsync(MSG_WARP) {
-            warpImageAsync()
+            warpImageAsync(inpaint)
         }
     }
 
@@ -755,6 +768,10 @@ class MainActivity : AppCompatActivity() {
         setContentView(binding.root)
         updateButtons()
 
+        binding.checkBoxInpaint.setOnCheckedChangeListener { _, _ ->
+            clearOutputImage()
+        }
+
         binding.buttonReset.setOnClickListener {
             binding.imageEdit.resetPoints()
         }

app/src/main/res/layout/activity_main.xml

@@ -44,6 +44,13 @@
                     android:textAllCaps="false"
                     android:textColor="@color/button_text" />
 
+                <CheckBox
+                    android:id="@+id/checkBoxInpaint"
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:layout_weight="0"
+                    android:text="Inpaint" />
+
                 <TextView
                     android:id="@+id/textView3"
                     android:layout_width="wrap_content"