i am developing an app, which display the curve colored like this and the length of it i can change (in code), but i don't know how to do that, can anybody help me:
Thank you !
Jerry Nixon posted a blog and walk through video on creating this exact same control.
It builds on a previous blog about building dials.
Related
I'm building an iphone photo app. I don't know how to achieve this kind of effect on an image:
When the user drags a finger across the arrow, I want the image to be distorted accordingly. How can I achieve this? Is there any framework that makes this process simple?
Thank you.
No clue about iOS, but the look reminds me of a thin-plate spline warp. It's quite easy to implement in OpenGL, a quick Google search for example code returns plenty of hits.
From the sound of it I think your looking for the CoreImage framework. Look into the various distortion effects...in particular CIBumpDistortionLinear.
I don't have any code so check out this tutorial and read up on CoreImage.
I'm investigating if it's possible to implement the same functionalities of ZBar library with iOS 7 api.
Everything was good so far thanks to this tutorial.
However, I now want to have a green box shown on the screen whenever the camera detects a QRCode. The green box is supposed to wrap around the QRCode.
From the delegate of AVCaptureMetadataOutput, I can grab AVMetadataObject but the bounds getting from this object is always very small which is not correct, given the fact that my QRCode is very big on the screen.
Anyone has any ideas on how to achieve the green focusing box?
P/S: I came across the documentation and couldn't understand this line "If the metadata originates from video, bounds
may be expressed as scalar values from 0. - 1.". This is for the bounds property of AVMetadataObject
You can look at this tutorial for qrCode scanning using iOS 7.
I had to do the same thing in my scanner app. Here is a link that I found very useful and pretty much answered all my questions.
He goes step by step from setting up the scanner to adding the bounding box.
I'm following this guide: http://www.aishack.in/2010/08/sudoku-grabber-with-opencv/2/
and modifying to iOS 5.0.
I managed to find the largest contour (the sudoku "board"), however, it only locates the surrounding square, without the lines inside, as in the tutorial. can this be easily solved?
I'll try and find a way around it, but still would like to know. thanks!
I assume that you are using the camera right now. Try to load the image what is used in the tutorial and check if your implementation works on that image. Then you can continue with nice sudoku images from the web. You may also change the camera angle and distance from the sudoku when taking pictures to get a better, clearer view.
I'm basically trying to work out how to take a slice of an image, say a screenshot of an iPhone home screen, slice out the first icon and compare it to a set array of images in a library. Any help on where to start?
I'm no iPhone programmer, but I might be able to suggest a few things:
The SURF feature detection implemented in OpenCV should help you with this
There is a nice article on using OpenCV in Objective-C code.
A quick & dirty way might be to use the difference blend mode which should return the difference between the 1st image(top) and the 2nd image(bottom). If there is no difference the result will be completely black. So, the more black pixels in the difference result, potentially, the more similarities between the compared images.
I'm not an iOS developer, so I don't know if there is an image library that ships with sdk or if there's a free/opensource library for basic image processing. Still this should be trivial to implement:
e.g.
- (int)difference((int)topPixel,(int)bottomPixel)
{
return abs(topPixel-bottomPixel);
}
Note: Syntax might not be correct :)
HTH
This may not help you with taking a screenshot of the iOS home screen... But these articles show how to take snapshots from within a UIKit application:
https://developer.apple.com/library/prerelease/ios/#qa/qa1703/_index.html
https://developer.apple.com/library/prerelease/ios/#qa/qa1714/_index.html
Perhaps you would instruct the user to press home-power (buttons) to take a snapshot and store in the photo roll, then load that screenshot into an app to process the screenshot.
Hope this helps!
I want to draw line on iPad using user points. How can I do that? Kindly reply if you know
For simple 2D graphics you'll want to use Quartz 2D.
This Stackoverflow question has some good examples, and apple provide full documentation here
Also - see this very similar question: How do I draw a line on the iPhone?
The accepted answer includes instructions and sample code.