I need to capture audio data from the computer mic, process it and then plot it in real time. Processing each frame will produce a 1-D array which I want to display in an image where each value in the array is mapped to a color. The next audio frame is processed similarly and is then displayed on the next row of the image and so on. In matlab, one can achieve this using imagesc function. I also want the user to be able to scroll up and down to see current or previous data.
I believe I will need to buffer the processed data in a file or database and then asynchronously update the plot as mentioned above.
I'm trying to achieve all the above using C#.
My question is: what is the best way to generate the image/plot? I've done a lot of research (Microsoft Chart, VTK, several codeproject articles..) but couldn't find exactly what I want.
Also, what would be the best database to use in such case?
I do not think that there is a component that does exactly the things you've described. In most frameworks/bundles all the images get visualized by native system calls (in the end) which accept strides, buffers and so on, driving all by HANDLE. So, either you generate next time new image with new rows or just draw it yourself by stacking prev image to new one.
Scrolling (AKA windowing) is not trivial but possible again with already pre-created image in memory which is fixed. However, please note, that GDI+ based images (.NET Bitmap) is kind of limited for more than 9000px size. Please consider using alternative like IPP, AForge images.
I recommend you draw rows yourself because in your task re-sizing in going to be an issue because of rows bluring.
So, all in all, you might need to do it yourself.
Related
I've been trying to find a way to show the stream of my webcam with a 30 second delay.
I found out that VLC is able to do this, but the problem is that the framerate is much too low and it's not smooth or viewable at all. I have to run this on a fairly old laptop with a better webcam that I own now, so I guess it's not an option.
I am able somewhat familiar with c#/c++ and python so I thought that I might make a solution of my own as the task seems fairly easy. Though, the problem is, I don't know where to start and any nudges in the right direction would be much appreciated.
My initial idea was to record first 30 seconds of the stream to the disk, then use VLC to view partial file (AFAIK it's able to do that). Is it an idea worth working on or should I scratch it and use some sort of a buffer for the video frames in the last 30 seconds?
Again, any nudges in the right direction will be much appreciated, thanks!
Take a look at OpenCV.
It can retrieve and show images from a webcam.
A lot a of tutorials are also available; e.g. http://opencv.willowgarage.com/wiki/CameraCapture
So simply create an array (or whatever) to hold the amount of pictures to be expected in 30 sec (FPS*30).
Start to retrieve images and as soon as the array is filled start to play from position 0.
Newly retrieved images can than be stored at the position from the "just" shown image.
Miguel Grinberg has written an excellent video streaming tutorial in Python which sends JPEG frames successively. Check his blog post here:
http://blog.miguelgrinberg.com/post/video-streaming-with-flask1
Each of these JPEG can be quickly reviewed and then broadcasted. [To take the required Delay in consideration]
As far as getting the input video feed is concerned, you can interface a webcam using OPENCV. OpenCV uses VideoCapture which returns raw images as bytes. These bytes needs to be encoded to JPEG and interfaced with Miguel's code.
import cv2
class VideoCamera(object):
def __init__(self):
# Using OpenCV to capture from device
self.video = cv2.VideoCapture(0)
def __del__(self):
self.video.release()
def get_frame(self):
success, image = self.video.read()
# We are using Motion JPEG, but OpenCV defaults to capture raw images,
# so we must encode it into JPEG in order to correctly display the
# video stream.
ret, jpeg = cv2.imencode('.jpg', image)
return jpeg.tobytes()
This approach will help you cater all the required features:
No internet required
Adjustable delay - Easily control the delay and the processing you want to perform on each frame
Good Quality
Record on Demand - Store the captured frames as per need
Have a record back feature, by just saving the previous 24*x frames (24fps stream)
I am trying to create a map application, something like google maps, that shows a portion of a large map and lets you navigate north east up west, zoom in and out, etc...
I encountered a critical problem in the beginning: XNA does not allow importing images larger than a top maximum size limit, even in HiDef mode. And my map image size is much larger than the limit.
I was thinking I could split the map (manually, in photoshop) into smaller pieces and paste them one by one in the game, so they will make up a the whole map.
Is there a better way to do that?
Yes. That is a better way of doing it.
If you wanted to get fancy, you could probably do it in a content processor / importer (rather than doing it manually each time the image changed).
This would involve creating a type that contained a collection of your tiles.
You'd then create a new content importer that could take an image file, and split it up into chunks (maybe of configurable size).
It would produce an instance of your newly create type which you could load at runtime.
Check out the Content Pipeline posts on Shawn Hargreaves' blog.
I have an objective: I need to join, for example 2 pictures like http://imgur.com/9G0fV and http://imgur.com/69HUg. In the result there has to be and image like http://imgur.com/SCG1X not http://imgur.com/LO4fh.
I'll explain in words: I have some images with the same areas and I need to find the area, crop it in one image and after this join them.
Take a look at this article, it's explains a possible solutions using the C# Aforge.NET image processing library
What you want to do is read the pixel values into arrays,
then find overlapping area using an algorithm like correlation
or min cut.
After finding coordinates of overlap, write out both images into
new array, use coordinates relative to large image minus
position of overlap in that source image plus position in destination image.
C# is not a factor in solving this, unless you meant
to ask about existing .NET frameworks that can help.
I am developing .NET library called SharpStitch (commercial) which can do the job.
It uses feature-based image alignment for general purpose image stitching.
I have 6 images
Each image is part of a 180 degree (or so) panorama. The images overlap. The task is to write a program in C# that will import the images, determine where the images overlap and merge the images together to form a single image.
Write the program in such a way that the user can import as many images as he or she would like to have merged into one image.
There should be some function in the program that will determine if given 2 images the 2 images overlap and to what amount.
Also, the input images may not necessarily be constructed from a strict linear axis of revolution, and their orientation may not be the same (you will need to consider rotation and both X and Y offsets to the overlap region as part of the program).
This is quite a large project. You might want to take a look at the source code for Hugin for inspiration. Unless you're really set on doing it yourself, you might just want to use (and possibly contribute improvements) to Hugin instead of starting over.
OTOH, Hugin isn't written in C#, so if that's a requirement, you probably will have to start over. Offhand I don't remember if the source to Autopano-SIFT is available, but if so it would be a good start (it already handles one of the most complex parts of the task).
I have an image gallery that is created using a repeater control. The repeater gets bound inside my code behind file to a table that contains various image paths.
The images in my repeater are populated like this
<img src='<%# Eval("PicturePath")' %>' height='200px' width='150px'/>
(or something along those lines, I don't recall the exact syntax)
The problem is sometimes the images themselves are massive so the load times are a little ridiculous. And populating a 150x200px image definitely should not require a 3MB file.
Is there a way I can not only change the image dimensions, but shrink the file size down as well?
Thanks!
I would recommend creating a handler that can resize images for you on the fly and encode them in whatever format you like.. kind of like a thumbnail generator. This will cost CPU on the server but you can cache images and severely reduce bandwidth costs ETC. Let me see if I can find the link to a good article I read on something similar.
You can look at this article it isn't the one I had read but it has some info about how you can go about implementing this.
You're looking for the GetThumbnailImage method of the Image class. You will either want to generate the thumbnail images ahead of time or create the image the first time it is accessed and save it to disk for later use (so first access would be slow but subsequent requests would be quick).
You could try either of these 2 projects on CodePlex.com, both offer dynamic image generation with caching.
Dynamic Image Process
ASP.NET Image Generation
The later is straight from Microsoft.