I need to enlarge an image but without resizing its pixels.
So if primal image is just a black square, then new image should be something like it:
How could I do that?
You could look into the Core Image "Dot Screen" filter or other filters in the "halftone" category of core image.
If you can't find something there, you might have to build it yourself by manipulating the bitmap contents directly.
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I am using CIDetector to find faces in a picture.
The coordinates of faces it returns are the absolute coordinates in the image file (The image dimensions are much larger than the screen size obviously).
I tried to use the converRect:toView command. The image itself is not a UIView so the command doesn't work, also I have a few views embedded inside each other where finally the image is being shown.
I want to convert the bounds of the found faces in the image to the exact location of the face being shown on the screen in the embedded image.
How can this be accomplished?
Thanks!
The image being shown on the phone - the image is scaled to fit the screen with aspect fit
The coordinates from CIDetecter (CoreImage) are flipped relative to UIKit coordinates. There are a bunch of tutorials out there on iOS Face Detection but most of them are either incomplete or mess up the coordinates. Here's one that is correct: http://nacho4d-nacho4d.blogspot.com/2012/03/coreimage-and-uikit-coordinates.html
One thing to note: the tutorial uses a small image so the resulting coordinates do not have to be scaled to the on-screen (UIImageView) representation of the image. Assuming you use a photo taken with the iPad camera, you will have to scale the coordinates by the amount the source image is scaled (unless you reduce its size before running the face detection routine -maybe not a bad idea). You may also need to rotate the image for the correct orientation.
There is a routine in one of the answers here for rotating/scaling: UIImagePickerController camera preview is portrait in landscape app
And this answer has a good routine for finding the scale of an image when presented by a UIImageView using 'aspect fit': How to get the size of a scaled UIImage in UIImageView?
You will need to use the scale in order to map the CIDetector coordinates from the full size image to the scaled down image shown in a UIImageView.
I have a rectangular NSImage A and I want to scale to embed into a squared transparent image B keeping A's ratio. So, in the end I'll get a squared image with the rectangle in it.
How can I compose that image?. I mean, how can I draw an NSImage over another NSImage and save the resulting image?.
I've been reading about clipping an NSImage inside a beizer but I need to keep ratio instead of filling the beizer square.
I hope you understand what I want.
Thanks.
The 'Cocoa Drawing Guide' has a section called 'Drawing to an Image'. From that documentation:
It is possible to create images programmatically by locking focus on an NSImage object and drawing other images or paths into the image context. This technique is most useful for creating images that you intend to render to the screen, although you can also save the resulting image data to a file.
There is example code there.
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.
My app downloads images from a website. These images are all manner of sizes, from 800x600 up to 1800x1600. I analyze the image using facial recognition, and then want to resize and crop the image. However, it's important that the detected CGRect be visible on the cropped image.
I was using the excellent UIImage+Resize code and using UIViewContentModeScaleAspectFill, but it doesn't seem to have a programatic way of specifying an arbitrary location that needs to be visible in the final image. So if a face is located at the 1600px range of an 1800x1600 image, it'll get cut off.
Is there an easy solution to this, or do I need to dig around in the depths of UIImage+Resize? Any guidance would be appreciated!
I am writing a Cocoa application for mac osx. I'm trying to figure out how to determine the size of an image that will be captured by a camera? I would like to know the size of the image that will be captured so I can setup a view with an aspect ratio that won't distort the image. For example, if my view is defined to be 640x360 and my camera captures images that are 640x480, the displayed image looks short and fat. I'm also displaying some other layers over the image and I need the image size to be able to scale and position the layers properly.
I won't know the type of camera that is attached until run-time so I'd like to be able to interrogate the device and get attributes like image size. Thanks for the help...
You are altering the aspect ratio of the image when you capture in 640x360 instead of 640x480 or 320x240. You are doing something similar as a resize, using the whole image and making it a different size.
If you don't want to distort the image, but use only a portion of it you need to do a crop. Some hardware support cropping, others don't and you have to do it in software. Cropping is using only portions of the original image. In your case, you would discard the bottom 120 lines.
Example (from here):
The blue rectangle is the natural, or original image and the red is a crop of it.