In some Ruby code which uses Cairo, I need to draw a number of fills over a single path. This is part of a graphics application, where multiple fills may be stacked on top of each other using different blend modes.
Each fill is drawn using fill_preserve to preserve the path so that the next fill can occur over the same path without retracing it. This is done somewhat like so:
rectangle_data.each do |rectangle_datum|
context.rectangle(*rectangle_datum.rectangle)
fill_data.each do |fill_datum|
context.set_source_rgba(*fill_datum.color)
context.fill_preserve
end
end
The problem is that this leaves the path even after all fills have taken place, which means that individual shapes are just drawn as one huge filled shape.
To solve this, I'd simply need to clear the current path manually, but I can't figure out how to do this. I've had a look through the documentation for Cairo::Context through Google Translate but I can't find it. (The docs are in Japanese!)
How can I manually clear a Cairo context's current path?
I had a look over Cairo::Context#methods and found #new_path, which does just what I'm after. So you can do:
rectangle_data.each do |rectangle_datum|
context.rectangle(*rectangle_datum.rectangle)
fill_data.each do |fill_datum|
context.set_source_rgba(*fill_datum.color)
context.fill_preserve
end
context.new_path
end
Related
This answer provides a nice way to make smooth animations in SciLab. I now have to write a simulation of a body attached to two strings (and therefore its movement regarding some additional forces).
The code in the link works well to render movement of a single point and, unfortunately, I didn't manage to make an animation of a point + two lines using this method. If someone is curious, I tried this code to do it:
frametime=(tk-t0)/Nt//defining the waitnig time
plot(Y(1,1),Y(2,1),"o")//plotting the point
plot([0;Y(1,1)],[0;Y(2,1)],style=1)
plot([D;Y(1,1)],[0;Y(2,1)],style=1)//plotting the two initial lines
h1_compound = gce();
h_point=h1_compound.children
h_point.mark_size = 20;
h_point.mark_background = 2;
h_line1=h_compound.children
h_line2=h_compound.children
//h_axes = gca();
//h_axes.data_bounds = [0,-1;10,1];
realtimeinit(frametime);
for i=1:Nt//my vectors have Nt points
realtime(i);//wait "frametime" seconds before drawing the new position
h_point.data=[Y(1,i),Y(2,i)];
h_line1.data=[[0;Y(1,i)],[0;Y(2,i)]]
h_line2.data=[[D;Y(1,i)],[0;Y(2,i)]]
end
The question is: is there any way to make an animation of three shapes without making axes blink (as it is with the window refreshment) or other wierd stuff?
Since you didn't create a MCVE I can't reproduce your exact problem. But you may try to add drawlater(); before, and drawnow(); after your data modification to see if it does help with blinking or not.
Or you may get much better looking result by saving your plots in every round with xs2gif and assemble the animation with another gifmaker progam (there are free online sites to do this, however with some limitations). If you need to present your result, you should do this step anyway.
Say I have a range – something like a 400x400 rectangle at 60, 60 – which is dynamically generated by a separate program. I'm wondering how it's possible to crop my document to that range in the command line?
Everything I've read has suggested I'd need to add a rectangle to the document, resize the document to that rectangle (resize to selection), and then remove the rectangle.
But I'm having trouble with adding and removing that rectangle. I found the ToolRect verb, but I can't seem to find anything related to actually drawing that rectangle (or removing it).
So, am I doing this wrong or is there just no way to add (and select) the rectangle using only the command line? Using another program is also fine, but I haven't had much luck with that (I couldn't get the python modules installed for the only possibly helpful thing I found..).
In this email discussion from 2012, someone said:
There is no way to pass parameters to verbs (with the current
implementation, they don't take parameters by design).
In case they add this capability later, the required verbs to crop the page would be:
EditSelectAll
SelectionGroup
ToolRect (requires parameters, i.e. where to crop)
EditSelectAll
ObjectSetClipPath
FitCanvasToDrawing
FileVacuum
FileSaveAs (requires a parameter, so that we don't have to overwrite the original)
Since Inkscape can edit any valid SVG, I'd rather look into other available SVG libraries, like this one for Python.
If you are OK with rasterising your image, take a look at this question. Inkscape unfortunately ignores the --export-area option when exporting to svg or pdf.
My – admittedly, unsatisfying – solution was to create a separate program to add a viewbox to the SVG text.
The program I made was implemented into a separate part of my project, so I don't have a good command line version, but if you plan on making one yourself, whatever XML editing library you have for your language of choice should be all you need. I used xmldom for Node.js with relative ease.
Problem: I have a scanned version of some tax report (e.g. https://docs.google.com/file/d/0B3TmJsb1vYhqclFFendvTlRoV28/edit?usp=sharing ), and I must fill it programmly. So, it`s needed to find empty areas and put to it some values in program.
Now I see only one solution - manually find coordinates of these empty areas, code it to program, and output values to these coordinates.
Is it possible to programmly find coordinates (may be by some pattern recognition or something else) of empty areas? May be use of some Ruby tools (e.g. Prawn) ?
So, there isn't complete automatic solution. I've solved this problem by searching areas to input, store its coordinates and then output to these areas
Is there a way to select the control points automatically in Matlab instead of manually selecting them by cpselect? Thank you very much.
I just recently worked on a project where I had to do the same thing -- eventually I found that you can select control points automatically, but only if you use automatic selection to find the control points for both the unregistered and the orthophoto. (The control points used to define image transforms are stored in matrices, so if you can get your automated system to output a set of point coordinates in matrix form you can pass them to straight to cp2tform and bypass cpselect entirely.) On the other hand, cpselect stores corresponding pairs of image points using some kind of special data structure, so that I was never able to just pass it a set of control points for one image while leaving the other image blank.
I don't have the Matlab Image Processing Toolbox, but I see from the documentation that cpeselect can be called with an argument specifying the initial set of control points. Can you reduce your task to automating the creation of that initial set?
I'm using the Prawn Ruby library (http://prawn.majesticseacreature.com/) to generate some pdf documents. I draw a table without any problem. Next, I want to insert some lines after the table for various people's signatures. Before I draw the lines, I would like to see if there is enough remaining room on the page to fit all the signatures. If not, I will start a new page and put the signature lines there. However, in order to determine if enough room remains on the page, I need to know what the current cursor position is after drawing the table. I can't for the life of me figure out how to do this. Any ideas?
Of course, after entering the question, I immediately figure it out. The 'y' and 'y=' methods in the Document class allow you to get and set the current y position, which is all that is necessary.