Archive for July, 2015

Improvements to the RendererKivy (Part 2)

July 22nd, 2015 No comments

The following modifications have been implemented in these days:

  • Fixed problem when rendering concave polygons. It can be seen from previous images that in the case of an arrow and a wedge there was a defect on the rendering due to the triangulation algorithm to fill it. The mesh renderer uses “triangle_fan” and since all the points form triangles always with the hub in concave polygons this was a problem. It was fixed by splitting concave polygons into convex ones. This was implemented using Tesselator a utility class in the graphics kivy package.
  • Path was being closed when it should not. It has been fixed that a path line was being closed by default, the initial point was removed so the line does not try to close a path when it is not necessary.
  • Elements out of the figure axes are not rendered. The problem here is that everything was being drawn in the same layer. A stencil widget is used as a mask so everything out of bounds it is hidden. In the second figure, 4 stencil instructions are created to show just the graphics instructions visible in the clip rectangle.
  • Focus behavior was added to the FigureCanvasKivy. Keyboard events are automatically bound by the focus behavior.
  • Added support for multiple dash length and offset in a same line. Line can receive a list with the values of length and offset for the respective rendering. For instance [10, 5, 20, 10] would create a line with 10 visible points then 5 hidden 20 visible and 10 hidden. This can be seen on the figure of the sin function below

dynamic dashes in a line4 stencil widgetsartist demointegral demo

Categories: GSOC2015, kivy, matplotlib Tags: , ,

Improvements to the RendererKivy

July 17th, 2015 No comments

The main improvements to the Renderer involved to run a test for the backend_kivy with as many as possible examples. From the test we figured out there were some implementations missed. The following are the main improvements done to the Renderer this week:

  • The rendering of the text is not blurry anymore. This was fixed by working with int values instead of float, it seems like opengl was trying to give some percentage of the pixel value to the previous and next pixel giving this effect.
  • Math text such as integrals, derivatives and so on can be added to the figure canvas. Matplotlib provides a very useful math text parser which receives the string and returns an object that can be embedded on the kivy canvas.
  • Images as textures can be added inside a Figure and outside as well. Matplotlib allows to generate some interpolation graphs which can be inserted into the axes and give some fancy visualization of data. Since color in kivy’s renderering is multiplicative, you would want the color to be white or the texture will be ‘tinted’ as it will be something other than 1.* color channel at pixel. Initially the problem was that the texture was invisible but it was solved by changing the Color to white as it is explained before. When a figure is not present the image is added directly to the canvas as a texture.

Some examples can be seen in the pictures below. Additionally there are two known problems, the first one is that the rendering is out of the axes and the second one is related to the path and mesh creation. This problems can be seen specifically in the integral example and the electric dipole with the arrows and magnetic fields.

gradient bar imshow without figure

Read more…

Categories: GSOC2015, kivy, matplotlib Tags: , ,

Navigation Toolbar for #kivympl using an Action Bar

July 17th, 2015 No comments

After my last post I started the implementation of a Navigation Toolbar for the backend. For the Navigation Toolbar for kivy we decided to experiment with an ActionBar from the set of kivy widgets. It is a very early version and not implemented at all, but this is a snippet of how it would be the layout and the result can be seen on the image below. The only element being used for now are the icons for the action buttons so we can have an idea of how it would look like.  The behavior of each one of the items will be defined on the callbacks. The NavigationToolbar2Kivy extends from NavigationToolbar2 which is the base class.

def _init_toolbar(self):
        basedir = os.path.join(rcParams['datapath'], 'images')
        actionbar = ActionBar(pos_hint={'bottom': 1.0})
        actionview = ActionView()
        for text, tooltip_text, image_file, callback in self.toolitems:
            if text is None:
                # insert a separator
            fname = os.path.join(basedir, image_file + '.png')
            action_button = ActionButton(text=text, icon=fname)
        self.canvas.add_widget(actionbar, canvas='after')

Navigation Toolbar Kivy MPL

Kivy matplotlib backend with right text positioning and rendering.

July 8th, 2015 No comments

In order to fix the problem of the layout of the text inside the canvas, an important function had to be overwritten with the information of the bounding box for each text inside it. The function is get_text_width_height_descent in this, one calculates the width and height and return them. Inside matplotlib these values are important to calculate the positioning of the elements according to the layout set by the user. Additionally, in the draw_text method transformations and styling is applied to the text. At the end we can have a working backend with different fonts and styles that are mapped between matplotlib and kivy capabilities.

Another inconvenient in the rendering of the graphs were some glitches while drawing. I was calculating u and v to create the mesh for the polygons when this was not really necessary. After some debugging and analysis of the vertices the final implementation generate the meshes and lines for all the elements in the canvas as follow:

Screenshot from 2015-07-07 12:18:28 example mpl kivy

As can be seen, now it is getting closer to how the static image implementation looks like from the previous post.