Line-Charts.md

@@ -13,12 +13,15 @@ The *LineChartRasterizer* currently uses the min and the max of the datasets to
 There is not much to say about the axis itself, the *LineChartRasterizer* does not use an arrow head to show continuity of the datasets because there is none. It ends with tha max value on the x axis which was present on the dataset. As for the tickmarksize, the *LineChartRasterizer* currently uses 2. 
 
 ## **Line rasterizing algorithm**
-The *LineChartRasterizer* currently uses the **bresenham** algorithm to draw a line between two datapoints as nearly to the ideal line as possible. Because **bresenham** assumes an equal distant grid, there is a conversion to be done between the geometrical position (for example in milimetres) and the dot position, measured in braillecell/ dots. The current implementation  looksup the nearest point, which is why there are sometime aritfact points.
+The *LineChartRasterizer* currently uses the **bresenham** algorithm to draw a line between two datapoints as nearly to the ideal line as possible. Because **bresenham** assumes an equal distant grid, there is a conversion to be done between the geometrical position (for example in milimetres) and the dot position, measured in braillecell/ dots. The current implementation  looksup the nearest point, which is why there are sometime aritfact points.  
+
+There is also the issue that on the canvas, the y coordinates grow bigger as they go down, but bresenham assumes that the origin of the y coordinates is in the left bottom corner.
+
 Here the code:
 ```java
     private void bresenham(final Double xStart, final Double yStart, final Double xEnd, final Double yEnd) {
-        int y0 = (int) (mCanvas.toDotRectangle(mCellLineArea).intWrapper().getHeight() - yStart);
-        int y1 = (int) (mCanvas.toDotRectangle(mCellLineArea).intWrapper().getHeight() - yEnd);
+        int y0 = (int) (mCanvas.toDotRectangle(mCellLineArea).intWrapper().getHeight() - yStart); // Conversion of the origin
+        int y1 = (int) (mCanvas.toDotRectangle(mCellLineArea).intWrapper().getHeight() - yEnd); // Conversion of the origin
         int x0 = (int) (xStart.doubleValue());
         int x1 = (int) (xEnd.doubleValue());
         int dx =  abs(x1 - x0);
@@ -49,5 +52,28 @@ Here the code:
 
 ## **Point rasterizing algorithm**
 To draw a line, one need a method to draw point. This is also done via a conversion between a geometrical view to a "braille" view.
+Here the code:
 
-
+```java
+    private SimplePointListImpl rasterizePoints(final PointList list, final double globalMinX, final double globalMinY) {
+        Objects.requireNonNull(list, "The given PointList for the rasterization of points was null!");
+        double xMin = globalMinX;
+        double yMin = globalMinY;
+        Iterator<Point2DDouble> iter = list.getListIterator();
+        Rectangle canvas = mCanvas.toDotRectangle(mCellLineArea);
+        double canvasStartX = canvas.intWrapper().getX();
+        double canvasStartY = canvas.intWrapper().getBottom();
+        SimplePointListImpl result = new SimplePointListImpl();
+        while (iter.hasNext()) { // iterate through all datapoints
+            Point2DDouble current = iter.next();
+            double currentValueX = current.getX() - xMin; 
+            double currentValueY = current.getY() - yMin;
+            double stepX = currentValueX / mDpiX;
+            double stepY = currentValueY / mDpiY;
+            result.pushBack(new Point2DDouble(round(canvasStartX + mXStepWidth * mCanvas.getCellWidth() * stepX), round(canvasStartY - mYStepWidth * mCanvas.getCellHeight() * stepY)));
+            mCanvas.getCurrentPage().setValue((int) round(canvasStartY - mYStepWidth * mCanvas.getCellHeight() * stepY), (int) round(canvasStartX + mXStepWidth * mCanvas.getCellWidth() * stepX), true);
+        }
+        result.calculateExtrema();
+        return result;
+    }
+```