Develop Reference

Using camera to analyze garage door status

I got the idea to use images from my IP camera, to register if my garage door is open or closed (or maybe even somewhere in between).
I figured it would be simple to put some identifiable markers on the door, and then "read" their position programatic, but I have no experince in image processing, and therefore no idea what it's called.
After a lot of reading, my guess is that I need to use Emgu CV in some way (I'm coding in C#).
Can someone point me in the right direction to get started?
What is the right method for what I am trying to achieve? Blob tracking?

I know this is old but I happen to have done exactly this recently.
I have an old smartphone from which I can remotely enable the LED flash + take a picture and download it. I attached a shiny reflector on a specific location of the garage door and the smartphone is drilled to the wall.
I implemented in python. I download the picture over HTTP, and after a few attempts I identified where to crop the full picture. Then I compute the brightness, which tend to indicate a valid detection above 150 (it's usually 200 when the reflector is here, 130 when it's not but lights on, and 10 when the reflector is not here and lights are off).
def loadFromCam(url):
print("GET " + baseUrl + url)
return requests.get(baseUrl + url, timeout=(10,10))
def brightness(im):
stat = ImageStat.Stat(im)
return stat.rms[0]
def loadImage():
response = loadFromCam("cam/1/frame.jpg")
f = open(destination + 'frame.jpg', 'wb')
f.write(response.content)
f.close()
return Image.open(BytesIO(response.content))
def cropImage(img):
left = 365
top = 400
right = 410
bottom = 435
return img.crop((left, top, right, bottom))
def toggleLed():
loadFromCam("cam/1/led_toggle")
and then how it's used:
toggleLed()
time.sleep(0.1)
image = loadImage()
toggleLed()
crop = cropImage(image)
crop.save(destination + "crop.jpg")
print("brightness:", brightness(crop))
The result is two files (full picture and crop), and the brightness amount.
Note: I just started Python so this may be ugly or not the recommended practice

Printing PDF programmatically bloats file size

Ok, So I've been given a task to build a light weight printing feature that will replace a third party tool that costs a significant amount of money,and not only that, has far too many features.
I've managed to build a little system that polls some data and calls an endpoint on an on-premise MVC app, which in turn prints the document.
All is great, but I'm really struggling to figure out why the PDF file size bloats when hitting the Print Queue.
Currently the File size is 822KB when I print manually via Adobe the PDF is compressed to 342KB
BUT using the system it bloats to an astonishing 4.22MB
To note I am using the PDFium SDK Nuget package to take away some of the heavy lifting. Having said that, I do utilize System.Drawing.Printing to craft settings to pass to PDFium.
A little code to demonstrate printing:
public bool PrintPDF(string printer,
string filePath)
{
try
{
var printerSettings = new PrinterSettings
{
PrinterName = "Hewlett-Packard HP LaserJet P2015 Series",
Copies = 1,
};
using (var document = PdfDocument.Load(#"C:\folder\Documentation\test.pdf"))
{
using (var printDocument = document.CreatePrintDocument())
{
printDocument.PrinterSettings = printerSettings;
printDocument.DefaultPageSettings = pageSettings;
printDocument.DocumentName = "test.pdf";
printDocument.PrintController = new StandardPrintController();
printDocument.Print();
}
}
return true;
}
catch(System.Exception ex)
{
new Email().SendEmail("", "TEST ERR", ex.Message, "email address");
return false;
}
}
At the moment I'd be happy if it printed the physical size (822KB) rather than bloating it.
Id really appreciate some guidance and a nudge in the right direction.

PDF is (usually) a vector representation of the page, its a page description. PDF can contain bitmap data as well, but for text and line art its usually vector, and white space simply isn't included in the description at all.
When you print, then behind the scenes the application creates a device context compatible with the printer you select, replays the drawing commands it used to draw the content on the display, and then tells the printer context to print.
That causes the device driver to be handed the GDI commands to draw the page. Depending on the printer type (ie what page description language it understands) the device driver can simply pass on the commands (for a GDI printer), convert them to a high level vector representation (like PostScript) or render them to a bitmap. Some drivers may do a combination of these approaches. The result is then sent to the printer.
The Adobe PDF 'printer' works by co-opting the Windows PostScript printer driver, which converts GDI commands into vector PostScript operations, which are easily turned into vector PDF operations, resulting in a small representation of the page.
It sounds to me like your printer (or possibly printer driver) is 'dumb' and wants, or is being sent, a big bitmap. Once upon a time, in the days when printers ran on serial interfaces and 9600 baud was fast, it was worth keeping the file size small and having the printer be smart, because it took a long time to send the data. Nowadays, that's less of a concern, even several megabytes can transfer rapidly, and if you send a pre-rendered bitmap to the printer, the printer can be dumb and still print fast, because all it has to do is transfer the bits.
You haven't really said what you mean when you "print manually using Adobe" or "use the system" so I can't tell you more than that, but my guess would be that your big PDF simply contains a large (compressed) image.

Increase fps in record video ffmpeg

I need to record 2 videos from 2 cameras in full hd 30 fps.
I use ffmpeg and wrapper - Aforge for c#.
init device:
_videoCaptureDevice = new VideoCaptureDevice(deviceName);
_videoCaptureDevice.VideoResolution = _videoCaptureDevice.VideoCapabilities[0];
_videoCaptureDevice.DesiredFrameRate = _fps;
_videoSourcePlayer.VideoSource = _videoCaptureDevice;
_videoCaptureDevice.NewFrame += _videoCaptureDevice_NewFrame;
_videoSourcePlayer.Start();
saving frames
if (_videoRecordStatus == VideoRecordStatus.Recording)
{
_videoFileWriter.WriteVideoFrame(eventArgs.Frame);
}
and init file writer
_videoFileWriter = new VideoFileWriter();
_videoFileWriter.Open(_fileName, _videoCaptureDevice.VideoResolution.FrameSize.Width,
_videoCaptureDevice.VideoResolution.FrameSize.Height, 30, VideoCodec.MPEG4, 10 * 1000 * 1000);
now _videoCaptureDevice.VideoResolution.FrameSize equals 1280x720 and 640x480 (for second device). But I already have problems with recording. Maximum fps is 24 for 480p and 13-14 for 720p (when I try to record videos from 2 cameras in the same time)
How to increase it?
Or it isn't possible? Maybe more powerfull computer will solve this problem (I have Pentium(R) Dual-Core CPU 2.50Ghz and usual videocart (Geforse 8500 GT) for working with two displays, usual hdd, usb 2.0)?
I will glad any help (maybe another library, but not language (c#))
PS
I already used Emgu.CV and faced with simular problems..

The framerate is limited by the hardware.
Use AMCap or GraphEdit to check what your camera really supports. It will depend on the choosen resolution and ouput format (higher resolution -> lower framerater).
Be aware that AForge always uses the highest value for all resolutions which can lead to oversampling (e.g.: AForge produces the rames at 60Hz, but the camera only supports 15Hz at the given resolution, so the images will mostly be duplicates. See here
Also use process explorer and a profiler to see how busy your CPU really is and what it is doing.

How many USB cameras can be accessed by one PC

I am just wondering how many USB cameras can be accessed by one desktop PC? Is there any limit? I am planning to create my own Windows application (using .NET) to capture around 10 USB cameras that are connected to my desktop PC. Is this possible?

The problem is not how many you can discover. On a single USB bus, ~127 could be possible.
But, a USB bus can only transfer a limited amount of bytes per second. So if you want to use more then one, you have to calculate the amount of bandwidth you have for the video stream.
Example :
A USB bus normally can deliver realistically ~35 MB/s. 640*480*2 bytes per pixel => 614400 bytes per frame. #30 FPS this is ~17 MB/s, so you can use 2 cameras simultaneously with this setup.

If that Actually, see code for connect 5 cams in to one computer( processor core i3, 8gb ram!!!) you need connect all cameras in to usb ports only on you'r computer!!!
git hub link

a bit late sorry :)
What i found out is that a single USB card is limited by the USB bandwidth. but..
if you add USB cards on the PCI you can get more cameras but...
most vendors do not bother to alter the USB card address the computer see so you need to buy USB to PCI cards from different vendors and try your luck.
I had the same problem with firewire.
here is my code for python. (thank other programmers on stackoverflow)
# show multiple usb cameras
import os
import cv2
import threading
import time
import datetime
#font for image writing
font = cv2.FONT_HERSHEY_SIMPLEX
fontScale = 1
fontColor = (255,180,180)
lineType = 2
SaveImage = True # if true save images
duration = [100,100,100,10,10] # time between image saves in sec
IMAGESAVEPATH = "C:/tmp/pix" # path for camera to store image to
ShowText = True #Show text on image - text will be saved with the image
#camera thread. here me make a thread and its functions
class camThread(threading.Thread):
def __init__(self, previewName, camID):
threading.Thread.__init__(self)
self.previewName = previewName
self.camID = camID
def run(self):
print ("Starting " + self.previewName)
camPreview(self.previewName, self.camID)
#camera main loop - here we init the specific camera and start it then have a window to show the image and we store the image to the right directory
def camPreview(previewName, camID):
cv2.namedWindow(previewName)
cam = cv2.VideoCapture(camID) #start the camera (the cameras are numbered by the order they are connected to the computer)
if cam.isOpened(): # try to get the first frame
cam.set(3,4000) #this will bring the largest frame set
cam.set(4,4000)
cam.set(5,1) #fps
time.sleep(2)
cam.set(15, -1.0)
rval, frame = cam.read() #read the image
else:
rval = False
TStart = time.time() # time for next image
mpath = os.path.join(IMAGESAVEPATH, str(camID)) #make sure the directory we save in exists, otherwise make it
print("try to make dir ", mpath, " T " , time.time())
if not os.path.exists(mpath):
os.makedirs(mpath)
cv2.namedWindow(previewName, cv2.WINDOW_NORMAL)
while rval: #if we get an image
height, width, channels = frame.shape
if ShowText: # write text on the image
caption = str(camID) + " - " + str(height) + " " + str(width) + " "
cv2.putText(frame,str(caption),(20,20),font, fontScale, fontColor, lineType)
cv2.imshow(previewName, frame) # show image in its window
#cv2.resizeWindow(previewName, 1280,960) # resize all windows removed ofer
rval, frame = cam.read() #raed next image
key = cv2.waitKey(20)
if key == 27: # exit on ESC
print("key pressed ", camID)
break
TDiff = int(time.time() - TStart) # time difference from last image
if (SaveImage and TDiff > duration[camID]): # Save if time passed
file_name = os.path.join(mpath, "T{:%Y.%m.%d %H-%M-%S}.jpg".format(datetime.datetime.now())) # make file name string
cv2.imwrite(file_name, frame)
print("\rsaved to : ", file_name)
TStart = time.time() #reset time to next image
cv2.destroyWindow(previewName)
# Create 5 threads as follows
thread1 = camThread("Camera 1", 0)
thread2 = camThread("Camera 2", 1)
thread3 = camThread("Camera 3", 2)
thread4 = camThread("Camera 4", 3)
thread5 = camThread("Camera 5", 4)
thread1.start()
thread2.start()
thread3.start()
thread4.start()
thread5.start()

[Edited]
Actually, see this article which explains:
Get List of connected USB Devices
I'm not sure there is a maximum. I will check and post back if I find out.
[Further Edit]
Can't find a documented maximum. Theoretically the ManagementObjectCollection should be able to hold millions of objects in it. If you ran into problems (which I doubt with 10 devices), you could just preallocate the collection size upon instantiation.
I've just ran a test and I can pick up over 10 USB devices through a hub. You should be fine.

Maximum limit for usb devices connected to one host - 127. So, you can connect up to 100+ devices and they would work fine (100+ - because hub is also active device and have own address).
Possibly, you try to access first (already active) camera and program fails, because camera already locked?

How to capture screen to be video using C# .Net?

I know there are lots of question like this.
But I don't want to use the Windows media encoder 9 because it's a problem to get one, and then it is no longer supported.
I know that, one possibility is to capture lots of screenshots and create a video with ffmpeg but I don't want use third party executables.
Is there are a .net only solution?

the answer is the Microsoft Expression Encoder. It is according to my opinion the easiest way to record something on vista and windows 7
private void CaptureMoni()
{
try
{
Rectangle _screenRectangle = Screen.PrimaryScreen.Bounds;
_screenCaptureJob = new ScreenCaptureJob();
_screenCaptureJob.CaptureRectangle = _screenRectangle;
_screenCaptureJob.ShowFlashingBoundary = true;
_screenCaptureJob.ScreenCaptureVideoProfile.FrameRate = 20;
_screenCaptureJob.CaptureMouseCursor = true;
_screenCaptureJob.OutputScreenCaptureFileName = string.Format(#"C:\test.wmv");
if (File.Exists(_screenCaptureJob.OutputScreenCaptureFileName))
{
File.Delete(_screenCaptureJob.OutputScreenCaptureFileName);
}
_screenCaptureJob.Start();
}
catch(Exception e) { }
}

Edit Based on Comment Feedback:
A developer by the name baSSiLL has graciously shared a repository that has a screen recording c# library as well as a sample project in c# that shows how it can be used to capture the screen and mic.
Starting a screen capture using the sample code is as straight forward as:
recorder = new Recorder(_filePath,
KnownFourCCs.Codecs.X264, quality,
0, SupportedWaveFormat.WAVE_FORMAT_44S16, true, 160);
_filePath is the path of the file I'd like to save the video to.
You can pass in a variety of codecs including AVI, MotionJPEG, X264, etc. In the case of x264 I had to install the codec on my machine first but AVI works out of the box.
Quality only comes into play when using AVI or MotionJPEG. The x264 codec manages its own quality settings.
The 0 above is the audio device I'd like to use. The Default is zero.
It currently supports 2 wave formats. 44100 at 16bit either stereo or mono.
The true parameter indicates that I want the audio encoded into mp3 format. I believe this is required when choosing x264 as the uncompressed audio combined in a .mp4 file would not play back for me.
The 160 is the bitrate at which to encode the audio.
~~~~~
To stop the recording you just
recorder.Dispose();
recorder = null;
Everything is open source so you can edit the recorder class and change dimensions, frames per second, etc.
~~~~
To get up and running with this library you will need to either download or pull from the github / codeplex libraries below. You can also use NuGet:
Install-Package SharpAvi
Original Post:
Sharp AVI:
https://sharpavi.codeplex.com/
or
https://github.com/baSSiLL/SharpAvi
There is a sample project within that library that has a great screen recorder in it along with a menu for settings/etc.
I found Screna first from another answer on this StackoverFlow question but I ran into a couple issues involving getting Mp3 Lame encoder to work correctly. Screna is a wrapper for SharpAVI. I found by removing Screna and going off of SharpAvi's sample I had better luck.