Corner points in fontforge (seemingly also known as "coins", shown as squares in the UI), can have zero, one, or two handles to control the direction of the outgoing lines. This fact is nicely explained in the manual, but I cannot find any hints on how to control the number of handles.
How do I change the number of Bézier handles of a corner point?
In my specific case I have a straight line between two corners, and I would like to change this line to "bulge outwards" a bit. I tried to add a "curve point" between the two corners, but this gives me a strange curve point with no handles, which seems to be functionally identical to just another corner.
The simplest way to make a line bulge is to grab the line and drag (ensure the surrounding corner points are not selected first). This will immediately turn it from a line into a curve, and create control points. If you want to turn it back into a straight line, select the surrounding corner points then right-click the line and choose "Make Line".
You could equally add a curve point between the corners (CTRL-ALT-click where you want to add) and then merge it back out of existence using CTRL-M. This will leave the line as is, but with control points available.
Note that control points won't display unless you have selected an adjacent corner point or curve point. You can make them always display by selecting View>Show>Control Points (Always).
Very occasionally you may encounter what looks like a line but is actually a curve in which the control points coincide exactly with the corner points. The above methods will work fine in this situation too.
Related
In plot3d2 and similar graphic functions of Scilab, is there a way to set the colour of the back (reverse, flip, inner) side of facets?
I'm trying to draw a part of a (rather crude) torus, and the result is OK except for one row of facets. I suppose that, because of the way I generate the mesh, those facets are oriented differently - whatever algorithm renders them on the screen follows their perimeter in the opposite direction compared to others.
Instead of poring over my code to try to mend the topology of my mesh, I'd rather make sure the facet orientation doesn't matter - just set both sides to my colour. It will also improve the looks of the ends of my torus, where the inside shows and, again, is in a colour I didn't ask for.
But, hard as I search the documentation, I cannot find any mention of the flip side of mesh facets.
Any clues?
The backface color is named "hiddencolor" in the properties of a surface entity (see https://help.scilab.org/docs/6.1.1/en_US/surface_properties.html). It can be changed a posteriori, for example:
[X,Y]=meshgrid(-1:0.5:1);
plot3d2(X,Y,X.^2-2*Y.^2)
gce().hiddencolor=color("red")
You can assign -1 (instead of above) to use the same color as the front facing patches.
However, if all your patches are facing wrongly, you can also transpose all your matrices in the plot3d2 call:
[X,Y]=meshgrid(-1:0.5:1);
plot3d2(X',Y',(X.^2-2*Y.^2)')
gce().hiddencolor=color("red")
I'm using FontForge. I'm modifying the lower case q to make a straight-stalked 9. The q has 2 logical parts, the stalk, and the 'c'. The 'c' is too big vertically. How can I scale it down vertically while keeping the vertical stroke widths the same (and not altering any of the horizontal dimensions)?
I'm a novice with FontForge, so please spell out your explanation and provide step-by-step instructions. Thanks for your help.
It sounds like you want to decrease the x-height of the 'q' without changing stroke widths.
Font-forge provides a built-in tool to achieve this: Element > Styles > Change X-Height. You might like to experiment with this, but in practice it gives you very little control over the results and I would rarely use it.
Instead I would achieve this by directly modifying the nodes of the paths.
First, I would ensure that InterpolateCPsOnMotion is enabled. Double-click the pointer tool in your toolbox to access this setting.
This will help ensure that curves scale correctly (rather than distort) as you move control points. Now, I would select the nodes at the top and sides of the bowl of the q:
and use the down arrow key to move them down about half the distance you wish to decrease the height by. Then I would deselect the nodes at the side of the bowl:
and lower the remaining nodes the rest of the distance:
You will need to check the resulting appearance and possibly make tweaks to get it perfect. Note that this or any scaling technique can subtly distort the axis of modulated strokes, which you may wish to correct.
This technique presupposes that nodes are sensibly placed at the vertical and horizontal extrema of the bowl, and that you don't have extra nodes between these extrema. If you are not in this happy situation, you can add extrema by ctrl-shift-x and you can remove surplus nodes by selecting them and ctrl-m. If you can't remove extra nodes without significantly changing the shape of the bowl, you'll just have to modify these nodes by eye.
Another point: you say you're working from a "c". I'm not sure whether you just mean the C-shape of the bowl of the q, or whether you mean you are copying the actual glyph 'c'. Note that it is rare that the bowl of a 'q' will have exactly the same shape and weight as a 'c'. Typically the stroke will be somewhat lighter to achieve the right visual grey, and especial care will be taken where it intersects the stem. Often the two shapes will differ substantially.
This seems to be a rather asked question - (hear me out first! :)
I've created a polygon with perlin noise, and it looks like this:
I need to generate a texture from this array of points. (I'm using Monogame/XNA, but I assume this question is somewhat agnostic).
Anyway, researching this problem tells me that many people use raycasting to determine how many times a line crosses over the polygon shape (If once, it's inside. twice or zero times, it's outside). This makes sense, but I wonder if there is a better way, given that I have all of the points.
Doing a small raycast for every pixel I want to fill in seems excessive - is this the only/best way?
If I have a small 500px square image I need to fill in, I'll need to do a raycast for 250,000 individual pixels, which seems like an awful lot.
If you want to do this for every pixel, you can use a sweeping line:
Start from the topmost coordinate and examine a horizontal ray from left to right. Calculate all intersections with the polygon and sort them by their x-coordinate. Then iterate all pixels on the line and remember if you are in or out. Whenever you encounter an intersection, switch to the other side. If some pixel is in, set the texture. If not, ignore it. Do this from top to bottom for every possible horizontal line.
The intersection calculation could be enhanced in several ways. E.g. by using an acceleration data structure like a grid, quadtree, etc. or by examining the intersecting or touching edges of the polygon before. Then, when you sweep the line, you will already know, which edges will cause an intersection.
I have a graph like:
I would like to generate a set of (x,y) pairs that correspond to points of this graph.
Maybe one for each horizontal pixel.
How would I go about doing this?
If I had the image in uncompressed bitmap format, maybe cropped to the actual graph, I could examine each vertical strip for the blackest point...
I would prefer to work in Python, but I'm interested in any technique.
I answered a question like this a while back. It should be fairly easy to detect the grid, from there you can get the pixel's coordinates relatively to the grid. However, it wasn't clear how to extract the numbers, which you need to do in order to get the the scale of the grid. Although, it might be possible fairly easily if you can match the font and font size (which might be possible via scaling). Otherwise, you'd have to enter the numbers manually.
To extract the grid, you'd start from the top right and move diagonally until you find the start of the grid. From there you can follow the vertical and horizontal lines (of the grid) until they end. This should allow you to say with fairly high probability where the outer rectangle of the grid is and what the x and y intervals of the grid are in terms of pixels. The blackest parts within the grid should do for finding the curve, but it may require some interpolation depending on how many data points you need/want.
It also may be useful to look into techniques for reversing anti-aliasing effects. Although, the uncompressed bitmap image may not need it.
I'm doing some image processing, and I need to find some information on line growing algorithms - not sure if I'm using the right terminology here, so please call me out on this is needs be.
Imagine my input image is simply a circle on a black background. I'd basically like extract the coordinates, so that I may draw this circle elsewhere based on the coordinates.
Note: I am already using edge detection image filters, but I thought it best to explain with a simple example.
Basically what I'm looking to do is detect lines in an image, and store the result in a data type where by I have say a class called Line, and various different Point objects (containing X/Y coordinates).
class Line
{
Point points[];
}
class Point
{
int X, Y;
}
And this is how I'd like to use it...
Line line;
for each pixel in image
{
if pixel should be added to line
{
add pixel coordinates to line;
}
}
I have no idea how to approach this as you can probably establish, so pointers to any subject matter would be greatly appreciated.
I'm not sure if I'm interpreting you right, but the standard way is to use a Hough transform. It's a two step process:
From the given image, determine whether each pixel is an edge pixel (this process creates a new "binary" image). A standard way to do this is Canny edge-detection.
Using the binary image of edge pixels, apply the Hough transform. The basic idea is: for each edge pixel, compute all lines through it, and then take the lines that went through the most edge pixels.
Edit: apparently you're looking for the boundary. Here's how you do that.
Recall that the Canny edge detector actually gives you a gradient also (not just the magnitude). So if you pick an edge pixel and follow along (or against) that vector, you'll find the next edge pixel. Keep going until you don't hit an edge pixel anymore, and there's your boundary.
What you are talking about is not an easy problem! I have found that this website is very helpful in image processing: http://homepages.inf.ed.ac.uk/rbf/HIPR2/wksheets.htm
One thing to try is the Hough Transform, which detects shapes in an image. Mind you, it's not easy to figure out.
For edge detection, the best is Canny edge detection, also a non-trivial task to implement.
Assuming the following is true:
Your image contains a single shape on a background
You can determine which pixels are background and which pixels are the shape
You only want to grab the boundary of the outside of the shape (this excludes donut-like shapes where you want to trace the inside circle)
You can use a contour tracing algorithm such as the Moore-neighbour algorithm.
Steps:
Find an initial boundary pixel. To do this, start from the bottom-left corner of the image, travel all the way up and if you reach the top, start over at the bottom moving right one pixel and repeat, until you find a shape pixel. Make sure you keep track of the location of the pixel that you were at before you found the shape pixel.
Find the next boundary pixel. Travel clockwise around the last visited boundary pixel, starting from the background pixel you last visited before finding the current boundary pixel.
Repeat step 2 until you revisit first boundary pixel. Once you visit the first boundary pixel a second time, you've traced the entire boundary of the shape and can stop.
You could take a look at http://processing.org/ the project was created to teach the fundamentals of computer programming within a visual context. There is the language, based on java, and an IDE to make 'sketches' in. It is a very good package to quickly work with visual objects and has good examples of things like edge detection that would be useful to you.
Just to echo the answers above you want to do edge detection and Hough transform.
Note that a Hough transform for a circle is slightly tricky (you are solving for 3 parameters, x,y,radius) you might want to just use a library like openCV