say I have these boxes, some of which are black and some white.
The image shows a U shape drawn with the black boxes. Now say I have a matrix of 1s and 0s (it can be a huge matrix) like this:
111111111111111111
111111111111111111
111111111111111111
111111111101111111
111111111101111111
111011111101111111
111011111101111111
111011111101111111
111011111101111111
111011111101111111
111011111101111111
111100000011111111
111111111111111111
which shows zeros forming roughly the shape shown in the image. The image and the matrix are just examples. The image is a screen shot of a software where we should draw patterns, which would then need to be located in given matrices (inside simple text files).
What I'm looking for is a guidance on how to get started on this, cuz I have never programmed anything related to pattern recognitions, which this problem clearly seems to be related to. This is all that I have to do, a pattern given, to be matched with matrix of 0s and 1s. I dont think I can write it on my own in a few days, I'm writing code in c# vs 2013, so hoping I can find some libraries that would let me achieve this with minimal dependencies. Thanks
I think you need to provide a bit more information on what exactly you're looking for. Are the shapes all letters or arbitrary shapes?
Whatever you're looking for I'd start with emguCV. It's a pretty comprehensive library that isn't too difficult to use.
EmguCV has a lot of OCR (optical character recognition) functions which should be able to pick out letters pretty well.
I don't have as much experience using it for arbitrary shape detection but I think SURF detection, something which emguCV also does, might be a good way to go. It attempts to match a given image with features in another image.
People never draw at the exact same place and scale as your stored data.
The things you want are often done with neural networks (its also in aforge).
But it might be hard to A understand it and B use it in your code.
So maybe you could try it like this, get the first position, then record the delta position.
Try to find long lines, and their next direction; store the general direction changes.
above sample would be "down right up", you might also store some length info.
Then there is some math to check how much different sets are, for example string comparisons distance of strings (like in php the levenshtein function); cant think of a levenshtein func in c# dough i dont think c# is that rich with string functions but once you see that i'm sure you can derive something for C#.
Related
I hope that this is not the wrong place for my question, however, when I don't have anywhere else to go, SO never lets me down.
I am looking for a way to convert any given polygon on a map, to a serpentine line string. I would like to pass the polygon as a geography data type (it could be a poly string) which then takes the polygon, and generates a line string covering the entire area of the polygon.
The below images illustrates perfectly what I want to achieve in the sense that I want to provide the blue polygon and I want the green path to be returned either as a collection of points or a geography data type:
Taken from https://robotics.stackexchange.com/questions/14539/generate-a-coverage-path-given-a-polygon-region
I have scoured the internet and cannot seem to find any code examples around how to get this done. I would like to do this in C# preferable but I am not too fussy about the language. Second to C# I can look at using SQL too or even Python as a last resort.
I have read countless articles on Path planning but they all seem to be overkill in terms of what I want to achieve.
Could anybody point me in any direction as to how I can achieve this? Any information or samples will be highly appreciated.
I have thought about breaking the polygon down to its boundary lines and draw a serpentine line string across it by manually checking if a given point is within the bounds of the polygon. Surely there has to be a more efficient way to achieve this? Maybe a ready made API of some sort?
I want to create tiles out of a equirectangular image. So I want the image to be split into 4 lateral faces+up and bottom. Does anyone know any library that I can import into my c# project and which is able to do something like this?
Depending on your original image format, System.Drawing.Bitmap.Clone(Rectangle, PixelFormat) should do the trick.
More information here.
EDIT:
First, let me say that this is not going to answer your question either (not even close), you're seeking a library that already exists for this purpose and I don't know of one personally.
Equirectangular projection is the same as plate carrée (wow, that's humbling), so it's a very simple projection to work with in code.
Here is an example of it's use in a GIS application. I don't know what your purposes are, but the math is the same.
One way to do it is to deproject each pixel then draw it on a new image, but understand that to do this you will still require some sort of projection because you're changing from 3 dimensions to 2 dimensions.
I wasn't able to find a good example, but an easier or faster way might be to first use a matrix transform (again, to change projections), then cut the image into the regions you need.
Like I said, this isn't an asnwer, but if nothing else it will give you more keywords to goggle for.
I am witting a project of image processing.
For some part of my project to find good threshold value I need to find peaks and valleys of image's histogram.
I am witting my project in C# .net
but I need Algorithm or sample code in any languages like(Java, C,C++,....) to understand the logic of that. I can convert to C# by my self.
any document or algorithm or piece of code...
thanks
It's hard to beat Ohtsu's Method for binary thresholding. Even if you insist on implementing local extrema searching by yourself, Ohtsu's method will give you a good result to compare to.
If you already have computed your histogram, to find peaks and valleys is computationally trivial (loop over it and find local extrema). What is not trivial is to find "good" peaks and valleys to do some segmentation/threshold. But that is not a matter of coding, it's a matter of modelling. You can google for it.
If you want a simple recipe, and if you know that your histogram has "essentially" two peaks and a valley in the middle ("bimodal" histogram) and you want to locate that valley, I have once implemented the following ad-hoc procedure, with relative success:
Compute all the extrema of the histogram (relative maxima/minima, including borders)
If there are only two maxima, AND if in between those maxima there is only one local minimum, we've found the valley. Return it.
Else, smooth the histogram (eg. a moving average) and go to first step.
My requirement is something like this:
Lets take there is a Bitmap with a big letter 'A'.
The Bitmap is two colors (Either Black or White).
I need to skeletonize the big 'A'. (see: http://en.wikipedia.org/wiki/Topological_skeleton)
Using "Medial Axis Transforming" algorithm.
I tried my best in googling but i ended up being lost in finding a C#, C++ or at least pseudo code implementation of this algorithm.
I would like if someone could help me on this.
This page http://www.cs.sunysb.edu/~algorith/files/thinning.shtml has some sources you may wish to review.
The following two articles are the ones where the Medial Axis Transform was first proposed, so I think that you can find the algorithm to implement there. Do not expect a C++/C# implementation though.
A transformation for extracting new descriptors of shape
Shape description using weighted symmetric axis features
For the first one I was able to find a URL to a pdf. For the second one you will have to have access to ScienceDirect to download.
Another approach that you can use to extract the skeleton of a shape is by the Image Foresting Transform (IFT). It consists in representing the binary image as a graph. I made an implementation of the skeletonization by IFT in Matlab using the following article:
Multiscale skeletons by image foresting transform and its applications to neuromorphometry
I have a game with infinity procedually generated terrain. I'm using 1/f noise for the height (I think this is perlin noise?). Anyway it looks nice, but its not very playable since it doesn't really have flat areas. Just decreasing the amplitude won't work since I still want a large variation in height. Does anyone know of a filter I can apply to the heightmap to encourage flat areas while keeping a large range of heights?
Written in C#
EDIT: I've realised that what I want is for steep gradients to become steeper, and for flat gradients to become flatter. The terrain needn't be realistic, just "fun" for an FPS.
I believe you need to use a smoothing function to get rid of the jaggedness of the terrain, if that seems to be your problem.
I only glanced through this page, but it may be a decent guide: http://www.float4x4.net/index.php/2010/06/generating-realistic-and-playable-terrain-height-maps/
Not sure if this would help, but you could make that a range of your function is transformed into a flat surface with a high probability. For example all results between 0.1 and 0.3 have a 80% probability of end as a 0.1 surface. This way you encourage flat surfaces but keep the high variability you want.
Simple noise is not enough to generate a good looking terrain. It's just one of the intermediate steps in a way more complicated process. You need to simulate some real world phenomena: temperature, erosion, precipitation, that sort of thing. It's a CPU-heavy process, usually, but well worth the effort. Here are some interesting links:
Dungeon League - read all of it. Great stuff.
http://www.dungeonleague.com/
World generation articles on The Chronicles of Doryen:
http://doryen.eptalys.net/2010/01/back-to-the-caves-world-generator/
http://doryen.eptalys.net/2010/01/the-cave-map-with-ice-floe/
http://doryen.eptalys.net/2010/01/the-caves-biome-map/
http://doryen.eptalys.net/2010/01/nifty-debug-maps/
http://doryen.eptalys.net/2010/01/improved-precipitation-map/
http://doryen.eptalys.net/2010/01/biomes-balancing-and-rivers/
http://doryen.eptalys.net/2010/01/rrt-rivers-until-i-get-something-better/
http://doryen.eptalys.net/2010/01/disco-time/
(You can download the generator too, but it's written in C++)
You need a "master random generator" that will decide what a new area should look like, with a frequency of your choosing. For mountains choose what you have already. For flats choose less noise.
You can filter by median filter then. it will flatten your surface. But it will destroy mountains. This is fine for relatively flat areas like hollows and plateaus. If you want sharp mountains (with fast and big height diff) you should apply this filter selectively.
You should look for more materials especialy on procedural textures and noise. Those three are related a lot. You should think about using more than one noise function with different parameters and combine them using different functions or operators.
To help your case, you can use one function to generate high-frequency noise and then multiply it by low-frequency noise. This will result in peaks where low-frequency noise is closer to 1 and flats where it is close to 0. Some kind of smoothing/erosion algorithm is cool too. But you will still need lot of trial and error and fine tuning your parameters to get at least usable results.
Some more complex terains may need over 10 noise functions with alpha blending or smoothing and such. Dont think you will get nice looking terrain from aplying simple filter.
What you can do for an easy and ok looking solution is to Evaluate the height you get from your noise map with a custom curve function.
For example you can make your curve map noise points from 0.1-0.3 to 0.1-0.15 and then from 0.3-1.0 to 0.15-1.0.
This way you still keep the actual roughness of the terrain but make it flatter.