I'm planing to build a program which sees the wall, and if it detects objects on wall, it plays specific music.
Because I'm new to Image Processing, I thought and searched some methods.
Just capture every frame, and if some kinds of conditions are completed, it conducts actions. (In this case, it plays music.)
Save a default image, and keep comparing it with every frame.
I don't know the name of the methods that I described above.
Anyway, I think it is more reasonable to use method 2, because it is less expensive for memory.
Would you give some advice for this problem?
If there is better method to solve this problem, could you give me that method?
Related
I am really new to image processing. Currently I am using openCV for processing my video stream.
I am trying to detect if something was added in the frame & if added is there way to keep track of it. I already had tried to use yolo but It is not limited to some object I might have any random object coming in frame.
Secondly, I tried to use background subtraction method, but I have some object which keeps moving.
Thirdly, I tried to use contours but the are not that much accurate enough.
Please guide. I already had invested a month in this task. I have no clue what to do.
let me start off by showing that I have this UIImageView set up in my ViewController:
Each one of the lines contains a UIButton for a body part. If I select a particular button, it will segue me appropriately.
What'd I like to do is, when the user taps (but doesn't release) the button, I'd like the appropriate body part to show like this:
I can achieve this using 2 options:
UIBuzierPath class to draw, but would take a lot of trial and error and many overlapping shapes per body part to get fitting nicely as similiar in a previous question: Create clickable body diagram with Swift (iOS)
Crop out the highlighted body parts from the original image and position it over the UIImageView depending on which UIButton selected. However there would only be one image per body part, but still less cumbersome then option 1.
Now, my question is not HOW to do it, but which would be a BETTER option for achieving this in terms of cpu processing and memory allocation?
In other words, I'm just concerned about my app lagging as well as taking up app size storage. I'm not concerned about how much time it takes to do it, I want to just make sure my app doesn't stutter when it tries to draw all the shapes.
Thanks.
It is very very very unlikely that either of those approaches would have any significant impact on CPU or memory. Particularly if in option 2, you just use the alpha channels of the cutout images and make them semitransparent tinted overlays. CPU/GPU-wise, neither of the approaches would drop you below the max screen refresh rate of 60fps (which is how users would notice a performance problem). Memory-wise, loading a dozen bezier paths or single-channel images into RAM should be a drop in the bucket compared to what you have available, particularly on any iOS device released in the last 5 years unless it's the Apple Watch.
Keep in mind that "premature optimization is the root of all evil". Unless you have seen performance issues or have good reason to believe they would exist, your time is probably better spent on other concerns like making the code more readable, concise, reusable, etc. See this brief section in Wikipedia on "When to Optimize": https://en.wikipedia.org/wiki/Program_optimization#When_to_optimize
Xcode have tests functionality built in(and performance tests too), so the best way is to try both methods for one body part and compare the results.
You may find the second method to be a bit slower, but not enough to be noticed by the user and at the same time a lot more easier to implement.
For quick start on tests here.
Performance tests here.
I have a 30fps Quicktime .mov of still images I created with AVAssetWriter. (It's only about 10 frames long). I would like the user to be able to slow it down using a UISlider to about 1fps, but when I adjust the AVPlayer .rate property from 1 down to 0, it doesn't get anywhere near 1fps, it just stops playback (because a 0 rate is effectively stopping/pausing it, which makes sense). But how can I slow the player down to about 1fps? I think I'd need to do some math to calculate the actual rate, but that's where I'm stuck. Would it end up being something like 0.000000000000001?
Thanks!
If this was a requirement of mine I would approach this as follows (also suggested by Inafziger in the comments). Use AVAssetReader and roll my own viewer for the images. This would give you precise control using a timer as stated in your comments. Make sure you reuse some preallocated image(s) memory area (you can probably get away with space for a single image). I would probably take a pull approach like CoreAudio. When you need an image pull it from some image buffer manager class which calls AVAssetReaders read function. This way you can have N buffers that will always be available. This may be a little overkill. I do believe AVAssetReader pre decodes some amount of the movie upon initialization. This is why I say you can more than likely just get away with using a single buffer for reading image data into.
From you comment about memory issues. I do believe there are some functions in the AVAssetReader and associated classes that use the create rule.
I have a broad but interesting OpenCV question and I'm wondering where to start.
I am looking for any strategies or white papers that might help.
I need to get the position of people sitting at a conference table from a fixed overhead view. Ideally, I will assign a persistent ID to each person, and maintain a list of people with ID and coordinates. This problem could be easy in a specific case - for example, if designed for a single conference room table - but it gets harder in the general case, especially with people entering and leaving the scene.
My first question: is it a detection or a motion tracking problem? Or some combination of the two?
Well it seems like both to me. I would think you would need to take a long average of the visible area which becomes the background. Then based on your background information you can track movement of other objects.
Assigning an ID may become difficult if objects merge together (at least as far as the camera is concerned) and then separate again, say someone removing a hat placing it down and placing it back on.
But all that in mind it is possible even if it presents a challenge. I once saw a similar project tracking people in a train station using a similar approach (it was in a lecture so I can't provide a link sorry)
ok, so apparently xna games can only run at 30fps, which is a shame, because our game on iphone looked alot better at 60...
at any rate, because the only way you can get information about the touch screen state is to get its current state, effectively this means you can only sample the touch screen at 30 fps.
even if our game has to run at 30fps, is there any way to get higher resolution sampling from the touch screen? maybe through callbacks? or by accessing a list of touch events with time stamps?
The function you are looking for is TouchPanel.GetState. It is a simple matter of calling this function at 60Hz.
To get 60Hz you could set Game.TargetElapsedTime to 1/60th of a second. This will give you two updates to every one draw (according to Shawn Hargreaves' post here) assuming you are VSyncing at 30FPS.
If you still want your game state updates to run at 30FPS (just doing touch input at 60FPS), then you could put those updates on a different thread. Start an update going on that thread on the first call to Game.Update, and wait for it to finish on the second one, and so on.
(You should note that normally XNA input must be done on the main thread (source). I assume this applies to Phone and to touch input.)
Alternately you could replace the Game class's timing yourself entirely (calling GraphicsDevice.Present yourself). It's not easy to do, but it's possible. A good place to start is to look at the Game class in Reflector.
(Disclaimer: I haven't tried any actual Phone-based development yet, so there may be some Phone-related gotchas I am unaware of.)
The sampling rate of 30fps is set for performance reasons.
Even if you could find a way to query for touches more frequently you still couldn't update the UI at a faster rate so I'm not sure what benefit you'd get.
Before spending too much time on trying to find a solution I'd test on an actual device to see how acceptable 30fps really is.