I was wondering how do software like GotoMeeting capture desktop. I can do a full screen (or block by block) capture using GDI but that just seems too wasteful to me. Also I have looked into Mirror devices but I was wondering if there's a simpler technique or a library out there which does this.
I need fast and efficient desktop screen capture (10p15 fps) which I am eventually going to convert into a video file and integrate with my application to send the captured feed over the network or something.
Thanks!
Yes, taking a screen capture and finding the diff between previous capture would be a good way to reduce bandwidth on transmission by sending the changes across only, of course this is similar to video encoding techniques which does this block by block.
Still means you need to do a capture plus extra processing for getting the difference, i.e, encoding it.
by using the Mirror devices you can get both the updated Rectangle that are change and also pointer to the Screen. updated Rectangle pointer point to all the rectangle that are change , these rectangle are the change rectangle that are frequently changing. filter out some of the rectangle because in one second you can get 1000 of rectangles.
I would either:
Do full screen captures, and then
perform image processing to isolate
parts of the screen that have changed
to save bandwidth.
-OR-
Use a program like CamStudio.
i got 20 to 30 frame per second using memory driver i am display on my picture box but when i get full screen update then these frame are buffered. as picture box is slow and have change to my own component this is some how fast but not good on full screen as well averge i display 10 fps in full screen. i am facing problem in rendering frames i can capture 20 to 30 frames per second but my rendering is 8 to 10 full screen frames in one second . if any one has achive rendering frames in full screen please replay me.
What language?
.NET provides Graphics.CopyFromScreen.
Related
i'm new to windows phone 8 and need your help to capture screen activities in a video. I've to make a video of the activities performing on screen?
one solution to this that strike in me is to capture the screen in image form by dispatching a timer at a instance of time but this is not a right way to do as i've to make a video of screen activities? suggest your opinion how to handle this problem.
There's no built in way of doing what you want.
You will need two things:
Do a dispatch timer as you describe
Find code that will encode these frames into a movie. That's not an API that the phone supports - you will need to find existing code and use it. I am not aware of such code existing, but I have only looked for it once or twice and not very hard. You could, potentially, create an MJPG which is a fairly simple video format, but even that's not trivial and the ending file size can be prohibitive.
What I'm trying to do:
I've added a splash screen to an application I'm creating for Windows Phone 7. I did this simply by replacing the pre-existing splash screen file with my own.
What goes wrong:
The splash screen is not displayed like it should be - it is being down sampled to an 8 bit image or something weird:
-
The image I'm using
-
The image that gets displayed
It's a bit hard to see depending on your monitor, but on a phone it's reasonably obvious. There are fuzzy greenish lines that appear - basically like the image is being down sampled or the quality worsened.
Any idea what I'm doing wrong, or what might be happening?
Thanks.
Try forcing the app to display images at 32 bits per pixel (instead of the default of 16)
Add an attribute of BitsPerPixel="32" to the app element in WMAppManifest.xml
See http://forums.create.msdn.com/forums/p/85960/520394.aspx#520394
The problem is that the gradient on your splash screen is causing banding, which you can solve by dithering. Robby Ingebretsen has an action for PhotoShop that you can use: http://nerdplusart.com/photoshop-action-for-windows-phone-7-dithering
I suspect the emulator. Run the emulator at full size or run the app on an actual device.
Windows Phone is currently only supporting a color depth of 16bit, causing especially some gradients displaying downsampled for 24bit images. Some first generation firmwares by HTC had a "bug" that also allowed 24bit. Theoretically it is just a registry key, but you cannot commonly change it. Microsoft has limited the color depth to 16bit for the benefit of performance, but as far as I knnow there are some second-generation models without this limitation now.
You may try to downsample the image in Photoshop to 16bit and optimize it for this color depth.
I have a custom UISlider and use the currentPlaybackTime to change values of an MPMoviePlayerController object.
The problem is when i scrub at a fast rate using the slider, it doesn't respond as fast as i would like..
Is there any better way to have a fast interactive scrubber for ipad? targeting from OS 3.2
Well there are two issues, only one you can control directly.
Multimedia-content is commonly compressed using some kind of delta-compression, hence quick and exact seeking is not a trivial task to cope with. As that is common and since you can not directly change that, you will have to live with it.
the only way to increase responsiveness for seeking on the content-side (when encoding) is reducing the gop-size - that is, less p-frames between the i-frames.
when using a slider or a similar control, you could, instead of directly connecting the current playback position with it, handle any manual changes in an indirect fashion. You could run a timer based job that, whenever the slider/scrubber has been moved, tries to adjust the playback position towards that new value. Once the player is seeking, prevent the scrubber from getting feedback from the current playback location but allow it once the player is in playing state again. That way the user does not directly experience the clunky seek feedback.
We would like to display very large (50mb plus) images in Internet Explorer. We would like to avoid compression as compression algorithms are not what CSI would have us believe that they are and the resulting files are too lossy.
As a result, we have come up with two options: Silverlight Deep Zoom or a Flash based solution (such as Zoomify). The issue is that both of these require conversion to a tiled output and/or conversion to a specific file type (Zoomify supports a single proprietary file type, PFF).
What we are wondering is if a solution exists which will allow us to view the image without a conversion before hand.
PS: I know that you can write an application to tile the images (as needed or after the load process) and output them; however, we would like to do this without chopping up the file.
The tiled approach really is the right way to do it.
Your users don't want to download a 50mb file before they can start viewing the image. You don't want to spend the bandwidth to serve 50 megs to every user who might only view a fraction of your image.
If you serve the whole file, users will eventually be able to load and view it, but it won't run smoothly for most of them.
There is no simple non-tiled way to serve just a portion of an image unless you want to use a server-side library like imagemagik or PIL to extract a specific subset of the image for each user. You probably don't want to do that because it will place a significant load on your server.
Alternatively, you might use something like google's map tool to provide zooming and scaling. Some comments on doing that are available here:
http://webtide.wordpress.com/2008/08/27/custom-google-maps/
Take a look at OpenSeadragon. To make a image can work with OpenSeadragon, you should generate a zoomable image format which mentioned here. Then follow starting guide here
The browser isn't going to smoothly load a 50 meg file; if you don't chop it up, there's no reasonable way to make it not lag.
If you dont want to tile, you could have the server open the file and render a screen sized view of the image for display in the browser at the particular zoom resolution requested. This way you arent sending 50 meg files across the line when someone only wants to get an overview of the image. That is, the browser requests a set of coordinates and an output size in pixels, the server opens the larger image and creates a smaller image that fits the desired view, and sends that back to the web browser.
As far as compression, you say its too lossy, but if thats what you are seeing you are probably using the wrong compression algorithm or setting for the type of image you have. The jpg format has quality settings to control lossiness, and PNG compression is lossless (the pixels you get after decompressing are the exact values you had prior to compression). So consider changing what you are using as compression, and dont just rely on the default settings in an image editor.
I would like to write a program that can mirror a portion of the main display into a new window. Ideally this new window could then be displayed on an external monitor. I have seen this uiltity for a flightsim that does this on a pc (a multifunction display extractor).
CLick here for a screenshot of the program (MFD Extractor)
This would be a live window ie. constantaly updated video display not just a static graphic.
I have looked at screen magnifiers or vnc clients for ideas but I think I need to write something from scratch. I have tried to do some reading on osx programing but where do I start in terms of gaining access to the display? I somehow need to extract the graphics from a particular program. Is it best to go near the final output stage (the individual pixels sent to the display) or somewhere nearer the window management stage.
Any ideas or pointers would be much appreciated. I just need somewhere to start from.
Regards,
There are a few ways to do this:
Quartz Display Services will let you get access to the video memory for a screen.
Quartz Window Services (a.k.a. CGWindow) will let you create an image of everything that lies below a window. If you create a borderless, transparent, empty, high-level window whose frame occupies an entire screen, everything below it will be everything on that screen. (Of course, you could create a smaller window in order to copy a section of the screen.)
There's also a way to do it using OpenGL that I never fully understood. That technique is demonstrated by a couple of code samples, OpenGLScreenSnapshot and OpenGLCaptureToMovie. It's more or less obsoleted by CGWindow, though.
Each of those will get you an image that you can then show or write to a file or something.
To show an image, use NSImageView or IKImageView. If you want to magnify it, IKImageView has a zoomFactor property, but if you want nearest-neighbor scaling (like Pixie, DigitalColor Meter, or xScope), I think you'll need to write a custom view for that (but even that isn't all that hard).