I'm looking for guidance on implementing a view that renders an NSAttributedString within a polygon with holes, wrapping and reflowing text to fit the geometry. It's not CoreText that's the issue, but the general problem of partitioning an irregular shape into an ordered sequence of squat rectangles.
Similar questions haven't been answered fully:
How to fill a shape with text in Javascript
https://stackoverflow.com/q/3048305
CoreText's CTFramesetter does not support rendering into a CGPath
https://stackoverflow.com/q/3813318
CoreText handles an unbelievable amount of the grunt work associated with text layout and display, so I can't help but suspect that I'm reinventing a wheel. For the purposes of this question, please assume that I can check the substring that fits within a given rectangle, taking into account word wrap and hyphenation.
Edit: I've since decided to just sweep left-to-right drawing as much as fits between boundaries. It looks a bit haphazard even though I'm breaking at natural word boundaries, so I'd still appreciate guidance on how other applications wrap text.
Edit #2: It looks decent now that it supports basic word wrap and avoids rendering very short lines. My question must have been too vague. Thanks for looking.
Edit #3: Amorya points out that CTFramesetter now accepts any CGPath.
I wrote a blog post about achieving text wrap with Core Text:
http://blog.amyworrall.com/post/11098565269/text-wrap-with-core-text
The feature is new in iOS 4.3 and MacOS X Lion. You can now firstly draw inside non-rectangular paths, and secondly pass in other paths to mask the flow (i.e. be the holes you wrap around).
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I have an idea for an app that takes a printed page with four squares in each corner and allows you to measure objects on the paper given at least two squares are visible. I want to be able to have a user take a picture from less than perfect angles and still have the objects be measured accurately.
I'm unable to figure out exactly how to find information on this subject due to my lack of knowledge in the area. I've been able to find examples of opencv code that does some interesting transforms and the like but I've yet to figure out what I'm asking in simpler terms.
Does anyone know of papers or mathematical concepts I can lookup to get further into this project?
I'm not quite sure how or who to ask other than people on this forum, sorry for the somewhat vague question.
What you describe is very reminiscent of augmented reality marker tracking. Maybe you can start by searching these words on a search engine of your choice.
A single marker, if done correctly, can be used to identify it without confusing it with other markers AND to determine how the surface is placed in 3D space in front of the camera.
But that's all very difficult and advanced stuff, I'd greatly advise to NOT try and implement something like this, it would take years of research... The only way you have is to use a ready-made open source library that outputs the data you need for your app.
It may even not exist. In that case you'll have to buy one. Given the niché of your problem that would be perfectly plausible.
Here I give you only the programming aspect and if you want you can find out about the mathematical aspect from those examples. Most of the functions you need can be done using OpenCV. Here are some examples in python:
To detect the printed paper, you can use cv2.findContours function. The most outer contour is possibly the paper, but you need to test on actual images. https://docs.opencv.org/3.1.0/d4/d73/tutorial_py_contours_begin.html
In case of sloping (not in perfect angle), you can find the angle by cv2.minAreaRect which return the angle of the contour you found above. https://docs.opencv.org/3.1.0/dd/d49/tutorial_py_contour_features.html (part 7b).
If you want to rotate the paper, use cv2.warpAffine. https://docs.opencv.org/3.0-beta/doc/py_tutorials/py_imgproc/py_geometric_transformations/py_geometric_transformations.html
To detect the object in the paper, there are some methods. The easiest way is using the contours above. If the objects are in certain colors, you can detect it by using color filter. https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_imgproc/py_colorspaces/py_colorspaces.html
I'm sure this is already answered somewhere, but I just don't know the correct terminology to search for.
Context: I'm developing some code to generate a PDF that is using a fairly low-level library. So I'm having to write some basic text layout and fitting routines that will break on word boundaries and fit the text within defined constraints (e.g., in a column or around a fixed block).
I'd like to a find a reasonably efficient approach for fitting text around an arbitrary shape; eg something like this:
(This example was taken from this blog post: http://blog.amyworrall.com/post/11098565269/text-wrap-with-core-text, that was an answer to this question: Rendering CoreText within an irregular shape)
I'm guessing I need to break the text down into a series of boxes and it then becomes a geometry problem of fitting boxes into the shape, but I'm struggling to find good explanations of suitable algorithms or approaches for this. Delving into browser engine layout code to see how they do it is a case of getting lost in all the detail.
By far the most elegant way to rotate a globe in d3 that I've seen is Jason Davies' version: https://www.jasondavies.com/maps/rotate/
Unfortunately his code is minified, and even if I un-minify it, I can't make heads or tails of it with all the variables and functions named with single letters. (It doesn't help that the page includes code to implement "naive" rotation, and also the zooming, which I don't need.)
Anybody know of a demonstration of this technique that doesn't obfuscate the code?
Try looking here: http://bl.ocks.org/KoGor/5994804. The only thing is that you need to start dragging on a land and not on a water.
You may disregard text in Russian (the code has comments in English), but you may also consider translating it and the linked article.
I'm sorry if my question is somewhat vague. It's been a few years since I did anything with Qt, and back then I never did any fancy image stuff. What I'm asking for below is just some general suggestions on which classes to consider using. I'm trying to avoid barking up the wrong tree from the very start.
The situation: I'm writing a Qt-based program in which I need to display a somewhat large (let's say 5000x5000) raster image. The user should be able to zoom (quickly) in and out, and pan around the image in a way similar to for example Google maps. So far, this is not very different from the Qt ImageViewer example, except perhaps for the requirement that zooming happens quickly. However, I need to draw on the order of 50k simple geometric shapes (let's say circles) on top of the image, and be able to add and remove some of these in a simple way. The circles should have the same size no matter the zoom level, and should thus either be redrawn whenever the user zooms, or should be drawn with vector graphics. Think of the circles as map annotations. These should look the same at any zoom level, and also behave nicely with respect to panning.
I guess my question is twofold:
Can Qt draw vector graphics on top of a raster image?
In general, which classes should I consider for the above?
Thanks in advance. I don't like answering vague questions myself, but maybe someone with experience with Qt's graphics capabilities has an answer.
I suggest you use QGraphicsView and friends for this. It helps handling all the view/world transformation and the vector items can be achieved with various QGraphicsItems.
You can change the sizes of the items whenever the zoom level changes to maintain constant apparent sizes.
I have a need to do some drawing using win32/GDI (Native, not .NET), and I've run into the following problem:
I need to draw lines that are "styled." For example, in the attached image, the line marked "A" is a straight line as far as my application data is concerned, it just needs to be drawn with the additional zigzag as a style. Of course, this is easy to do programatically, but it gets more complicated when the line can be at any angle ("B") or even a bezier curve ("C").
Now, I could do this all programatically, painstakingly doing the math to put a zigzag around each line possibility, but that will take a lot of time and, more importantly, be rather error prone.
Is it possible to just give windows/GDI a "style" to apply to the line, perhaps a bitmap like the one marked "D", and have it use that as a pen to draw the lines? If not, is there a more flexible and less error-prone way of doing this than writing a bunch of specific drawing code for each of the "styled" lines?
*Apparently first timers can't post images. Examples can be found at http://i.imgur.com/IC0T2.png
This is not possible in Win32 GDI. You will need to do the math yourself.
It should be noted however, that you can obtain the points used to make up the line or curve which should make it substantially easier.
See this "Hit-Testing" tutorial for an example.
http://msdn.microsoft.com/en-us/library/ms969920.aspx
For a bezier curve you would use Path Functions:
BeginPath
PolyBezier
EndPath
FlattenPath
For straight lines you could use:
LineDDA
As far as I know there's nothing in GDI or even GDI+ that would support this. The only line options you have are dash-patterns, compound-pens, dash caps, end caps, and fill brushes.
You might be able to trick one of those functions into drawing something vaguely akin to your wiggles for straight splines, but it definitely won't work for curved splines.
It shouldn't be too hard to do this however. Sure, it will take a day or so, but all you have to do is write a line and bezier interpolator, divide the curves into equal segments, find the tangents at all those segments and alternate left and right. You'll end up with an array of points which can be drawn very quickly as a polyline.
There's nothing that'll do this automatically. You'll have to write some code. You might want to look at the LineDDA API in GDI. It might simplify the math your code will need.
ExtCreatePen(), maybe? I don't know for a fact if it supports zigzagging...