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).
Related
For a screen sharing collaborative app, it is desirable to give the remote party a mouse cursor also.
Is it possible to leverage NSCursor?
If not, I guess I must create a small accurately positioned top-level window displaying a bitmap (I've asked here if there is some way to retrieve the bitmaps from the system cursors).
Code/link contributions appreciated. If I figure it out first I will (as always) answer my own question.
I don't remember how it started, although I believe it began after using 3D tools at one point. I was looking for TWO answers, if possible:
For some reason, I find this hard to describe in words, so following the description is a link to a screenshot.
When I open, or create a new image followed by pasting an image from the Clipboard, in Photoshop, there is this zone at the top-left of the image window containing a smaller image, which is surrounded by an area that appears to be transparent - but when clicked on, or the window itself is moved, this "picture-in-picture" feature disappears - then comes back after the dragging is finished.
SCREENSHOT: http://i.imgur.com/MJq8I1W.jpg
1) What is this "feature" named?
2) How do I turn it off?
Thank you!
I don't think I can tell what you hit, or where this is located from the image you shared... can you upload a more comprehensive interface snapshot? It feels like you simply have a duplicate layer on top of your main layer...
Perhaps take a look at your workspace settings and try going to essential and see if that preview panel goes away.
I would like to access the whole contents of a Mac OSX screen, not to take a screenshot, but modify the final (or final as possible) rendering of the screen.
Can anyone point me in the direction of any Cocoa / Quartz or other, API documentation on this? In a would like to access manipulate part of the OSX render pipeline, not for just one app but the whole screen.
Thanks
Ross
Edit: I have found CGGetDisplaysWithOpenGLDisplayMask. Wondering if I can use OpenGL shaders on the main screen.
You can't install a shader on the screen, as you can't get to the screen's underlying GL representation. You can, however, access the pixel data.
Take a look at CGDisplayCreateImageForRect(). In the same documentation set you'll find information about registering callback functions to find out when certain areas of the screen are being updated.
I need to develop a desktop application which will
1.) have a list of the Different Application logos (Background Transparent) e.g. IE, FIREFOX, CHROME, PHOTOSHOP ETC.
2.) User will take a screenshot of desktop and save the image.
3.) Now my application need to search all the logos in the screenshot image and tell which all logos are present and where.
4.) I used OPENCV, it's working, but when user changes the desktop background & captures screenshot, it's not working as the transparent area of logo is getting the desktop background content.
Can somebody provide a solution or libraries open source, commercial to do this job.
This is easy to do using cross-correlation.
See my answer to this question.
Basically:
Start with desktop image and one template image for each icon
Apply edge detection (e.g. Sobel) to the desktop image and template images.
Throw away the original desktop image and templates, you won't need them anymore cause we'll be using the edge-detected images
For each template
Do template matching as you normally would
Threshold the maximum of the result. If it's above the threshold, you have a match at that position. Otherwise, no match.
If your icons are aligned in a grid on the desktop, you may be able to speed up your processing by only checking those specific grid positions.
EDIT
You can also save a lot of time by knowing which icons to search for. If you have access to the file system, then just look for *.lnk files (or any other extensions you may be interested in) in the directory that corresponds to the desktop (can't remember exactly what it is, but for Windows7 it's something like c:\users\misha\desktop). That will tell you what icons are there on the desktop. This will allow you to shorten your template candidate list before you go and do the template matching.
I like misha's answer and I think it should work for you. But it that doesn't work you could try replacing the transparant pixels in your reference logo with uniformly distributed random noise before trying the match. This will make the transparant pixels irrelevant for any matching computation because they will match just as bad no matter what there is on the desktop in those pixels.
I'm not familiar with the tools you're using, but I'm guessing you have to either:
a) Tell your program to ignore transparent pixels in the icon images during the comparison operation.
OR
b) Tell your program to treat transparent pixels in the icon images as "wildcards" which can be any color.
Pardon my frustration. I've asked about this in many places and I seriously don't think that there wouldn't be a way in Windows 7 SDK to accomplish this.
All I want, is to capture part of a 'child window' ( setParent() ) created by a parent. I used to do this with bitblt() but the catch is that the child window can be any type of application, and in my case has OpenGL running in a section of it. If I bitblt() that, then the OGL part comes blank, doesn't get written to the BMP.
DWM, particularly dwmRegisterThumbnail() doesn't allow thumbnail generation of child windows. So please give me a direction.
Thanks.
It's been a while since I did any of this, so my explanation might be a bit vague, but from what I remember, the Windows doesn't "see" the OpenGL rendered inside the window.
What Windows does is create the window at the specified size and then "hands it over" to OpenGL for rendering. This means that you can't get at the pixels as rendered from the Windows side of the code.
When we wanted to capture the 3D we had to re-render the screen to an off screen bitmap which was then saved (or printed).
Obviously a whole screen capture (Print Screen) works because it's reading the final pixels.
I suggest that you:
Forget the Thumbnail part of the task (in terms of capture).
Calculate where your window is.
Capture full screen.
Excise the area you are interested in (using data from step 2).
Rescale to the appropriate thumbnail size.
Sorry, its more work, but it should work, which is better than what you have right now.
This may help:
http://code.google.com/p/telekinesis/source/browse/trunk/Mac/Source/glgrab.c?r=140
http://www.codeproject.com/KB/dialog/screencap.aspx
Also Java's Robot class (http://java.sun.com/javase/6/docs/api/java/awt/Robot.html#createScreenCapture%28java.awt.Rectangle%29)
I don't have access to the source code of any child window that may be open including the one with OpenGL