ANImageBitmapRep

This is a class that I have been working on for a while now. It was originally made only for managing the bitmap data of a UIImage, but has evolved quite a bit throughout the years that I have used it. It currently allows for scaling, access ti bitmap data, drawing (using core graphics), cropping, rotating, and more. Because ANImageBitmapRep encapsulates a CGContextRef, it's easy to throw in your own image manipulation code simply by drawing on the CGContextRef.

The History

A while ago (in 2009) I decided that I needed a way to access the bitmap data of an image. This was when ANImageBitmapRep was born. I original created this class based on the existing Cocoa class, NSBitmapImageRep, which is not available on the iPhone.

This simple class later evolved due to my needs while using it in different apps. Most of the time when I make an app that uses this, I end up adding something to the class that was not there before. It was silly of me to not post this to GitHub a long time ago, because I find myself using ANImageBitmapRep constantly, and I bet other people out there could use it too!

In July, 2011, I decided to re-structure my Image Bitmap Rep classes to be more organized as well as more efficient. My remake included adding various levels of subclasses to ANImageBitmapRep which provide basic to advanced functionality. The ANImageBitmapRep class provides a few miscellaneous features, but mainly takes its functionality from its subclasses.

In October, 2011, someone challenged my implementation of ANImageBitmapRep, demoting the cascading subclass architecture. They modified the code to use categories, all to have me deny their pull request. Instead, I refactored my code, creating a new structure for subclassing, etc. Now, composition is used for all manipulators, and ANImageBitmapRep simply forwards messages to any number of manipulators. This structure also allows you to work with a single manipulator, without worrying about any methods that may be on ANImageBitmapRep or other manipulators.

Later that same month, Apple released Xcode 4.2 complete with Automatic Reference Counting. At this time I ported all of ANImageBitmapRep and the demos to work when compiled with and without ARC enabled. This was done using conditional statements along with the __has_feature(objc_arc) macro.

Later that same weekend, I decided that, since the code was already cluttered with conditional statements, I might as well add Cocoa (Mac OS X) support. I created a Mac target with several demos similar to the iOS demos, and changed around a couple of methods to use a new type, ANImageObj. When compiled for iOS, ANImageObj is actually a typedef of UIImage, whereas it is NSImage for Mac targets.

The Usage

In order to use an ANImageBitmapRep for an image, you have to create one first. This can be done either by using an existing UIImage, or creating a blank ANImageBitmapRep with given dimensions. Both can be done through the following initializers:

- (id)initWithImage:(ANImageObj *)image;
- (id)initWithSize:(BMPoint)sizePoint;

Interacting with bitmap data has never been as easy as it should. That's why ANImageBitmapRep provides simple functions to get and set individual pixels at any given location in the bitmap. The BMPixel structure holds RGBA values, and is generally what is used for interacting with pixels. For instance, getting the pixel at (0,0) on a bitmap looks something like this:

BMPixel pixel = [image getPixelAtPoint:BMPointMake(0, 0)];
NSLog(@"Red: %f", pixel.red);
NSLog(@"Green: %f", pixel.green);
NSLog(@"Blue: %f", pixel.blue);

Let's say we get a pixel, and we want to set the red value to be 100%. We can change our pixel and set it in the bitmap like this:

pixel.red = 1;
[image setPixel:pixel atPoint:BMPointMake(0, 0)];

Once you are finished interacting with bitmap data, you can get a UIImage from a bitmap with the -image method:

UIImage * anImage = [image image];

How about scaling, cropping, and resizing you might ask? ANImageBitmapRep provides all of those features as easy-to-use methods. The -setSize:, -setSizeFittingFrame:, and -setSizeFillingFrame: methods are good for all kinds of resizing and scaling. For instance, if we have an ANImageBitmapRep that is 100x100 pixels large, and we want to stretch it to 300x200, we could do:

[image setSize:BMPointMake(300, 200)];

You can read more about the -setSize*: methods in ScalableBitmapRep.h. Cropping is done in a similar manner. Let's say we have an image that is 200 by 200, and we want to cut out the middle 50 pixels of it (which would be {(75, 75),(50, 50)}). We can do this with the -cropFrame: method.

[image cropFrame:CGRectMake(75, 75, 50, 50)];

Finally, what is an image if it's not spinning around in a nauseating way? In RotatableBitmapRep.h you will see a method called -rotate:. This method takes a value from zero to 360 that represents an angle. Let's say we have an image that we want to rotate by 120 degrees. We can simply do the following:

[image rotate:120];

Well, that concludes our basic usage overview. You can find more information on some of these methods in their headers. I follow a strict Doxygen/Javadoc format for function descriptions, so it should be pretty simple to read what each of them do.

What Is That "oldies" branch?

Before I did my remake, ANImageBitmapRep was one class that implemented all of the features that it provided. After I did my remake, I found that most of the methods and calls to ANImageBitmapRep must be formed differently, and therefore the remake is not compatible with the original. This is to say that you can't throw in the new ANImageBitmapRep and expect it to work with your old ANImageBitmapRep code. The oldies branch contains the old version of ANImageBitmapRep (if I actually managed to make branches work :O), and should not be used in new projects.

When Will I Add To It?

Every time I make a new app that requires something new from ANImageBitmapRep, I make an addition to the class. A classic example is when I was making my app Zoomify. I needed a way to crop a part of an ANImageBitmapRep, so I added the cropWithFrame: method. This means that whenever I am working on an app that needs a new image-related feature, you can expect to see an update to this class!

Good Examples?

The Xcode project included with this code is a demo of what ANImageBitmapRep is capable of. It doesn't include a demo of all the features, but it shows off the simpler things that you can do with it. I will definitely be adding more demos to this project in the future, so stay tuned!

License

This is under the BSD 2-clause license.

License

unixpickle/ANImageBitmapRep

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