I'm trying to get the cover image of a DVD as a rectangular image from a photo. Now as the cover on the photo is usually a bit skewed I need to rectify it programmatically.
I've already removed most of the surroundings using the Laplacian of Gauss filter, but now I need to find the borders of the cover and somehow fill the whole frame with the coverimage.
I thought of using the Hough-Transformation, but this seems to be pretty brute-force for linking edges. I want to run this on a Windows RT Device (Surface), so a low-level idea for C# would be great. Any ideas?
You should look into OpenCV and the image segmentation parts. After that you can perform a skew / shear transformation on the 2D image.
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We're developing system of getting combined image from camera, which being moved by step motors to make pictures of the whole area. The problem is that when we combine separate frames, the edges are not accurate because of step motors discretization. So we came up with idea to make frames with little overlap, so we can put them over each other to get continual image with no blanks. We're using c# + LeadTools. So I'm wondering is there any option in Lead Tools (or maybe some other sdk) to detect areas, which are equal on both images, so we can stitch them correctly? Thanks in advance.
C# newbie here so please forgive me if my terminology isn't quite correct.
As part of this project, I have a user hold up a piece of paper to a webcam so I can capture, isolate and then eventually display back what they've drawn on it. I've put some restrictions on where the corners of the paper have to be in order for the program to accept it, but there's still the chance that it's distorted by perspective.
Here's an example image that I've captured and isolated the paper out of: image
What I want to be able to do is to distort this image so that the corners of the piece of paper are turned back into a 8.5x11-proportioned rectangle (as if the user had scanned it rather than held it up to the webcam). Rotation and skewing can only get me so far, ideally I would be able to freely transform the image, like in Photoshop. I found this example, I am basically trying to do the opposite. Curious if anyone's had to do this, before I start trying to reverse that four-point image distortion example.
This is sometimes called a Quadrilateral warp.
Disclaimer: I work for Atalasoft.
Our DotImage Photo SDK can do this and it's free. Look at QuadrilateralWarpCommand. You need to know the source and destination quadrilateral.
I'm working on a project where I need to take a single horizontal or vertical pixel row (or column, I guess) from each frame of a supplied video file and create an image out of it, basically appending the pixel row onto the image throughout the video. The video file I plan to supply isn't a regular video, it's actually just a capture of a panning camera from a video game (Halo: Reach) looking straight down (or as far as the game will let me, which is -85.5°). I'll look down, pan the camera forward over the landscape very slowly, then take a single pixel row from each frame the captured video file (30fps) and compile the rows into an image that will effectively (hopefully) reconstruct the landscape into a single image.
I thought about doing this the quick and dirty way, using a AxWindowsMediaPlayer control and locking the form so that it couldn't be moved or resized, then just using a Graphics object to capture the screen, but that wouldn't be fast enough, there would be way too many problems, I need direct access to the frames.
I've heard about FFLib, and DirectShow.NET, I actually just installed the Windows SDK but haven't had a chance to mess with and of the DirectX stuff yet (I remember it being very confusing for me a while back when I messed with it). Hopefully someone can give me a pointer in the right direction.
If anyone has any information they think might help, I'd be super grateful for it. Thank you!
You could use a video rendered in renderless mode (E.g. VMR9, EVR), which allows you to process every frame yourself. By using frame stepping playback you can step one frame each time and process the frame.
DirectShow.NET can help you to use managed code where possible, and I can recommend it. It is however only a wrapper to DirectShow, so it might be worthwhile to look for more advanced libraries as well.
A few sidenotes: wouldn't you experience issues with lighting which differs from angle to angle? Perhaps it's easier to capture some screenshots and use existing stitching algorithms?
i've been working on a webapp. i got stuck here in a problematic issue.
i'll try to explain what im trying to do.
here you see first big image which has green shapes in it.
what i want to do is to crop those shapes into different png files and make their background transparent like the example cropped images below the big one.
The first image will be uploaded by user and i want to crop into pieces like the example cropped images above.it can be done with GD library of php or by a server-side software written in python or c#. but i dunno what this operation called so i dunno what to google to find information. it is something to do with computer vision detecting blobs and cropping them into pieces etc.
any keywords,links would be helpful.
thanks for helps
A really easy way to do this is to use Flood Fill/Connected Component Labeling. Basically, this would just be using a greedy algorithm by grouping any pixels that were the same or similar in color.
This is definitely not the ideal way to detect blobs and is only going to be effective in limited situations. However, it is much easier to understand and code and might be sufficient for your purposes.
Opencv provides a function named cv::findContours to find connected components in an image. If it's always green vs white, You want to cv::split the image into channels, use cv::threshold on the blue or the red channel (those will be white in the white regions and near black in the green region) with THRESH_BINARY_INV (because you want to extract the dark regions), then use cv::findContours to detect the blobs. You can then compute the bounding rectangle with cv::boundingRect, create a new image of that size, and use the contour you got as a mask to fill the new image.
Note: These are links to the C++ documentation, but those functions should be exposed in the python and C# wrappers - see http://www.emgu.com for the latter.
I believe this Wikipedia article covers the problem really well: http://en.wikipedia.org/wiki/Blob_detection
Can't remember any ready-to-use solutions though (-:
It really depends on what kinds of images you will be processing.
As Brian mentioned, you could use Connected Component Labeling, which usually is applied to binary images, where foreground is denoted by white pixels and background by black pixels (or the opposite). The problem is then how to transform the original image to a binary one. If all images are like the example you provided, this is straightforward and can be accomplished with thresholding. OpenCV provides useful methods:
Threshold
FindContours for finding contours of connected components
DrawContours for extracting each component individually into a separate image
For more complex images, however, all bets are off.
I have a ton of pdfs scans that I have converted to images. Most of these scans contain a lot of whitespace around the edges.
What is the best way to go about finding a boundingbox for the actual content and then subsequently removing the whitespace?
I've thought about writing a program that just displays the image, then you drag a box and its saves the image, and moves on to the next one. This would be VERY time consuming, but it would get the job done. I'd like to be able to automate this process somehow using C#.
Either buy just cropping the image or by perhaps by suggesting a bounding box.
Emgu CV (on SourceForge) is a .NET wrapper around OpenCV, which has numerous image manipulation capabilities, including image filters and a bounding box algorithm that could solve this pretty easily.
http://code.google.com/p/aforge/
Aforge is a complete C# library Not a wrapper. OpenCV is very professional tool in compare of AForge.
Are you talking about scanned documents or scanned photos ? What format are your images in ? It sounds like you need an AutoCrop function.
Here is a freeware C# component that has an autocrop function. It should work well on B/W documents. You will need to see if it works the way you want if you are using photos.
http://www.hi-components.com/nievolution_features.asp
This component would also allow you to write code to load your images, draw a bounding box and and then save the cropped images as needed.