I need to create a very simple image cropping interface for an OS X cocoa application, but I am not sure where to start. The user needs to be able to choose a crop size from a menu of presets, be presented with a cropping rectangle that can be resized preserving the ratio, and moved around the image until they finally apply the selected crop to the image.
I've done some searching for sample code and projects but not found anything too useful. Core Image fun house has some pointers but is a retired sample. There are lots of iOS examples, but I've not found an easy to follow Mac OS example.
Can someone point me in the right direction (or at a sample project or framework!!).
Thanks a lot.
Here is a project you can look at:
https://github.com/foundry/drawingtest
It's a little demo I made as I was trying to understand the relationship between the rects in this method:
- (void)drawInRect:(NSRect)dstRect
fromRect:(NSRect)srcRect
operation:(NSCompositingOperation)op
fraction:(CGFloat)delta
Note that the older compositeToPoint: methods are deprecated and should not be used for this sort of thing.
srcRect is the portion of the original image (in it's own coordinates) that you want to keep.
dstRect is the rect that you want that cropped area to draw into.
JMRect in the project is an NSObject representation of an NSRect - so that we can use cocoa bindings to tie the interface controls together.
For your UI, the cropping rectangle could just be a transparent subview view with a border that you push around and resize over the image you want to crop.
This is by no means a complete solution to your question, but it's something you can poke around with - it might help you to get started.
Related
I am currently attempting to create an interactive, informative poster, with regards to Anti-Aliasing techniques and effects. The application is written in Obj-C within Xcode, and makes use of OpenGL and Cocoa functionalities.
I am attempting to create a small animation to display the difficulties of drawing a diagonal line on a pixel grid, however am having real trouble getting my head around the animation aspect.
I am aiming for something with a similar look and feel to this:
I have currently drawn a grid using OpenGL primitives:
,
and would like the effect above to be replicated within my grid, however without the shading yet (that is the next part), so just plain black pixels coloured step by step along the line.
I am new to both OpenGL and Obj-C, so am unsure whether best to implement the animation within OpenGL, or using OSx Core Animation - neither of which I have used before.
The OpenGL drawing takes place within my MyOpenGLView class, with the drawing done in a drawAnObject method, which is then called within the drawRect method.
Any help would be much appreciated, thanks in advance!
I am having a cocoa application for mac in objective c.
I am slightly new to mac application.
In my app, I want to implement growing imageview animation like shown below in the images.
As seen from the screenshots, when my window loads, I have some data to feel as it increases its value.
From 0 to the maximum value.
It should show like its rising from 0 to the values that I have specified.
I have seen lots of circular animations but didn't get much idea from that.
please give me suggestions on this.
Please ignore if mistakes as I am new to mac development.
Thanks in advance.
You should create mask and apply it to NSImageView layer object using the only image (one for 100%).
Read following article and don't be afraid it's about iOS-development, CoreAnimation is available in Cocoa too.
I am working on drag and drop activity for iPad. I have a rectangle PNG image (see the image named as obj2). When I drag obj1 only on the black portion of the rectangle then it should react.
if (CGRectIntersectsRect(obj1.frame, obj2.frame))
{
NSLog(#" hit test done!! ");
}
Right now, this piece of code takes hit test even on the transparent area. How to prevent that to happen?
For something as simple as your specific example (triangle and circle), the link that David Rönnqvist gives is very useful. You should definitely look at it to see some available tools. But for the general case, the best bet is clipping, drawing, and searching.
For some background, see Clipping a CGRRect to a CGPath.
First, create an alpha-only bitmap image. This is explained in the above link.
Next, clip your context to one of your images using CGContextClipToMask().
Now, draw your other image onto the context.
Finally, search the bitmap data for any colored pixels (see the above link for example code).
If any of the pixels colored, then there is some overlap.
Another, similar approach (which might actually be faster), is to draw each image into its own alpha-only CGBitmapContext. Then walk the pixels in each context and see if they ever are both >128 at the same time.
I have been looking for the solution on the web for a long time. Most tutorials are fairly simple about adding shadow to a UIView. I also noticed that if we add a shadow to an UIImageView. The shadow shape could perfectly fit the shape of the content image if the image itself has alpha channel in it. Say for example, if the image is an animal with transparent background, the shadow shape is also the same as that animal (not a rectangle shadow as same as UIImageView frame).
But these are not enough. What I need to do is to add some changes to the shadow so it may have some rotation angle and compressed (squeezed or shift) effect so that looks like the sunlight comes from a certain spot.
To demonstrate what I need, I upload 2 images below, which I captured from the Google Map App created by Apple. You can imagine the Annotation Pin is an image which has the Pin shape, so the shadow is also "pin shaped", but it is not simply "offset" with a CGSize, you can see the top of the shadow is shifted right about 35 degrees and slightly squeezed the height.
When we tap and hold and pin, the shadow is also animated away from the pin, so I believe that such shadow can be made programmably.
The best shadow tutorial I can found so far is http://nachbaur.com/blog/fun-shadow-effects-using-custom-calayer-shadowpaths But unfortunately, that cannot make this effect.
If anyone know the answer or know any better words to search for, please let me know. Thank you.
(Please note that the shape of the image is dynamic in the App, so using any tool like Photoshop to pre-render the shadow is not an option.)
In order to create dynamic effects like this, you have to use Core Graphics. It's incredibly powerful once you know how to use it. Basically you need to set a skew transform on the context, set up a shadow and draw the image. You will probably have to use transparency layers as well.
It doesn't sound like you can use CALayer shadows, since that is meant to solve a specific use-case. The approach Apple takes with the pin marks on the map is to have two separate images that are created ahead of time (e.g. in Photoshop) and they position them within the map relative to a reference point.
If you really do need to do this at run-time, it should still be possible by using either Core Graphics or ImageKit. To get a blurred shadow appearance, you can use the kCICategoryBlur CIFilter. You can then convert the image to grayscale. And to get that compressed look you just need to resize and skew the image.
Once you have two separate images, you can either take the CGImageRef for the shadow image and can set that as the content of another sublayer, or you can add it as a separate view.
If you know what all the shapes are, you could just render a shadow image in Photoshop or something.
So I want to have a view (NSView, NSOpenGLView, something CG related?) which basically displays a map. Such as:
http://dump.tanaris4.com/map.png
Obviously that looks horrible, but I did it using an NSView, and it draws SO slow. Clearly not designed for this.
I just need to allow users to click on the individual (x,y) coordinates to make changes, and zoom into a certain area (to see it better).
Should I go the OpenGL route? And if so - any suggestions as to how to get started? (I was able to follow the guide to draw a triangle, so that's good).
I did find this post on zooming in an NSView: How to implement zoom/scale in a Cocoa AppKit-application
My concern is if I'm drawing over 6000 coordinates and the lines connecting them, this isn't efficient at all.
I don't think using OpenGL would be of any good here. The problem does not seem to be the actual painting, but rather the rendering strategy. You would need a scene graph of some kind to dynamically handle level of detail and culling.
Qt has all this packaged in a nice class class QGraphicsScene (see http://doc.qt.nokia.com/latest/qgraphicsscene.html for reference, and http://doc.qt.nokia.com/main-snapshot/demos-chip.html for an example).
Some basic concepts you should consider using:
http://en.wikipedia.org/wiki/Scene_graph
http://en.wikipedia.org/wiki/Quadtree
http://en.wikipedia.org/wiki/Level_of_detail
Try using core graphics for this, really there is so much that could be done. Watch the video Practical Drawing for iOS Developers from WWDC 2011 and it should give an over view of what can be done with CG.
I believe even CoreGraphics will suffice for what you want to achieve, and that should work under a UIView if you draw the rectangle of your view completely under the DrawRect method of your UIView (you must overload this method). Please see the UIView Class Reference. I have a mobile application that logs points on the UIMapKit, kind of like Nike+, and it certainly works well for massive amounts of points/line segments. There is no reason why this simple approach cannot work for you as well.