Merge pull request #5765 from Ultimaker/log_litho

Logarithmic lithophane thickness

plugins/ImageReader/ConfigUI.qml

@@ -143,6 +143,52 @@ UM.Dialog
             }
         }
 
+        UM.TooltipArea {
+            Layout.fillWidth:true
+            height: childrenRect.height
+            text: catalog.i18nc("@info:tooltip","For lithophanes a simple logarithmic model for translucency is available. For height maps the pixel values correspond to heights linearly.")
+            Row {
+                width: parent.width
+
+                Label {
+                    text: "Color Model"
+                    width: 150 * screenScaleFactor
+                    anchors.verticalCenter: parent.verticalCenter
+                }
+                ComboBox {
+                    id: color_model
+                    objectName: "ColorModel"
+                    model: [ catalog.i18nc("@item:inlistbox","Linear"), catalog.i18nc("@item:inlistbox","Translucency") ]
+                    width: 180 * screenScaleFactor
+                    onCurrentIndexChanged: { manager.onColorModelChanged(currentIndex) }
+                }
+            }
+        }
+
+        UM.TooltipArea {
+            Layout.fillWidth:true
+            height: childrenRect.height
+            text: catalog.i18nc("@info:tooltip","The percentage of light penetrating a print with a thickness of 1 millimeter. Lowering this value increases the contrast in dark regions and decreases the contrast in light regions of the image.")
+            visible: color_model.currentText == catalog.i18nc("@item:inlistbox","Translucency")
+            Row {
+                width: parent.width
+
+                Label {
+                    text: catalog.i18nc("@action:label", "1mm Transmittance (%)")
+                    width: 150 * screenScaleFactor
+                    anchors.verticalCenter: parent.verticalCenter
+                }
+                TextField {
+                    id: transmittance
+                    objectName: "Transmittance"
+                    focus: true
+                    validator: RegExpValidator {regExp: /^[1-9]\d{0,2}([\,|\.]\d*)?$/}
+                    width: 180 * screenScaleFactor
+                    onTextChanged: { manager.onTransmittanceChanged(text) }
+                }
+            }
+        }
+
         UM.TooltipArea {
             Layout.fillWidth:true
             height: childrenRect.height

plugins/ImageReader/ImageReader.py

@@ -3,6 +3,8 @@
 
 import numpy
 
+import math
+
 from PyQt5.QtGui import QImage, qRed, qGreen, qBlue
 from PyQt5.QtCore import Qt
 
@@ -46,9 +48,9 @@ class ImageReader(MeshReader):
 
     def _read(self, file_name):
         size = max(self._ui.getWidth(), self._ui.getDepth())
-        return self._generateSceneNode(file_name, size, self._ui.peak_height, self._ui.base_height, self._ui.smoothing, 512, self._ui.lighter_is_higher)
+        return self._generateSceneNode(file_name, size, self._ui.peak_height, self._ui.base_height, self._ui.smoothing, 512, self._ui.lighter_is_higher, self._ui.use_transparency_model, self._ui.transmittance_1mm)
 
-    def _generateSceneNode(self, file_name, xz_size, peak_height, base_height, blur_iterations, max_size, lighter_is_higher):
+    def _generateSceneNode(self, file_name, xz_size, peak_height, base_height, blur_iterations, max_size, lighter_is_higher, use_transparency_model, transmittance_1mm):
         scene_node = SceneNode()
 
         mesh = MeshBuilder()
@@ -99,12 +101,14 @@ class ImageReader(MeshReader):
         for x in range(0, width):
             for y in range(0, height):
                 qrgb = img.pixel(x, y)
-                avg = float(qRed(qrgb) + qGreen(qrgb) + qBlue(qrgb)) / (3 * 255)
+                if use_transparency_model:
-                height_data[y, x] = avg
+                    height_data[y, x] = (0.299 * math.pow(qRed(qrgb) / 255.0, 2.2) + 0.587 * math.pow(qGreen(qrgb) / 255.0, 2.2) + 0.114 * math.pow(qBlue(qrgb) / 255.0, 2.2))
+                else:
+                    height_data[y, x] = (0.212655 * qRed(qrgb) + 0.715158 * qGreen(qrgb) + 0.072187 * qBlue(qrgb)) / 255 # fast computation ignoring gamma and degamma
 
         Job.yieldThread()
 
-        if not lighter_is_higher:
+        if lighter_is_higher == use_transparency_model:
             height_data = 1 - height_data
 
         for _ in range(0, blur_iterations):
@@ -124,6 +128,13 @@ class ImageReader(MeshReader):
 
             Job.yieldThread()
 
+        if use_transparency_model:
+            divisor = 1.0 / math.log(transmittance_1mm / 100.0) # log-base doesn't matter here. Precompute this value for faster computation of each pixel.
+            min_luminance = (transmittance_1mm / 100.0) ** (peak_height - base_height)
+            for (y, x) in numpy.ndindex(height_data.shape):
+                mapped_luminance = min_luminance + (1.0 - min_luminance) * height_data[y, x]
+                height_data[y, x] = base_height + divisor * math.log(mapped_luminance) # use same base as a couple lines above this
+        else:
             height_data *= scale_vector.y
             height_data += base_height
 

plugins/ImageReader/ImageReaderUI.py

@@ -34,6 +34,8 @@ class ImageReaderUI(QObject):
         self.peak_height = 2.5
         self.smoothing = 1
         self.lighter_is_higher = False;
+        self.use_transparency_model = True;
+        self.transmittance_1mm = 50.0; # based on pearl PLA
 
         self._ui_lock = threading.Lock()
         self._cancelled = False
@@ -75,6 +77,7 @@ class ImageReaderUI(QObject):
 
         self._ui_view.findChild(QObject, "Base_Height").setProperty("text", str(self.base_height))
         self._ui_view.findChild(QObject, "Peak_Height").setProperty("text", str(self.peak_height))
+        self._ui_view.findChild(QObject, "Transmittance").setProperty("text", str(self.transmittance_1mm))
         self._ui_view.findChild(QObject, "Smoothing").setProperty("value", self.smoothing)
 
     def _createConfigUI(self):
@@ -144,3 +147,11 @@ class ImageReaderUI(QObject):
     @pyqtSlot(int)
     def onImageColorInvertChanged(self, value):
         self.lighter_is_higher = (value == 1)
+
+    @pyqtSlot(int)
+    def onColorModelChanged(self, value):
+        self.use_transparency_model = (value == 0)
+
+    @pyqtSlot(int)
+    def onTransmittanceChanged(self, value):
+        self.transmittance_1mm = value