Camera image orientation

I was having a confusing problem where images taken from the iPhone camera were being displayed in the wrong orientation. I would take a photo in portrait and save the data to disk. Later when I retrieved the photo it would show up rotated 90 degrees.

The iPhone knows what orientation a photo is taken, and this orientation depends on how the camera is being held when you snap the photo. You can get the orientation value on a UIImage from the property imageOrientation.

When you save the photo, it is possible that this information could get lost, depending on the way you save it. If it does get lost, the UIImageView will assume the photo was taken as a left-side landscape photo, and display it with that orientation.

I ran into a problem when trying to save the camera image with UIImagePNGRepresentation(). For some reason this loses the orientation info. I switched to UIImageJPEGRepresentation() and all is well now.

So basically if you run into the problem, you have 2 choices: Be sure you use a format that preserves orientation data, or rotate the UIImage data directly before saving it to a file.

Rotating view around arbitrary point the easy way

I have a UIImageView that I want to rotate around a given point. By default, the layer will rotate around the center of the UIImageView. Trying to change this anchor point involves a bit of work, either move at the beginning and reposition all the view elements, or translating the view, rotating, and translating back. The last option works fine, unless you are trying to use core animation to smoothly rotate the view.

I found out a much easier solution to the whole problem. You could call it a workaround, but it works well without disturbing the view you want rotated.

Basically, you create a new UIView. Place the center point where you want the rotation to occur. Change the size of the view so that the view you want rotated will fit inside. Make your view (you want rotated) a subview of the new view. Now, just rotate the new view, and your subview will be rotated correctly.

Example: lets say we have a UIImageView that is 320x480 (the size of the whole iPhone screen). We want it to rotate from the bottom center instead of its middle. Create a new UIView that is 0,0,320,960. This is basically double the height of the screen, positioned so the bottom half is off the screen, which places the center point right where we want it. Now place your UIImageView inside the new UIView in the top half (visible on the screen.) Now when you rotate the UIView, it will pivot on the bottom center of the screen, and your UIImageView will rotate along with it, as expected.

OS X "burning" image to USB flash drive

I recently downloaded an Ubuntu image for netbooks, and I needed to install this onto a USB flash drive so I could boot it. This is pretty simple with OS X and Disk Utility and dd from the command line. Be sure your flash drive is large enough to hold the disk image.

* Plug the flash drive into a USB port and launch Disk Utility.
* Select the flash drive and press apple+i to bring up the info
* remember the device id, it will be diskN where N is a number, such as disk4
* select the volume (not the device) and click unmount.
* open a terminal window, and type:


sudo dd if=/path/to/file.img of=/dev/disk4 bs=1024


Be sure to use your path to the image file, and the device id you got from disk utility in place of "disk4". You can drag the .img file into the terminal window if you don't want to type the full path to it.

Now wait a bit for the image to be written. When its done you will get something similar to this:


969568+0 records in
969568+0 records out
992837632 bytes transferred in 521.666371 secs (1903204 bytes/sec)


Prediction: First Consumer Petabyte Hard Drive?

The first hard drive I owned came with my Amiga 1200, circa 1990. It held 40 megabytes of data, and I believe it was a $500 option. Yes, I said option. The computer happily ran on floppy disks alone, if you so desired. You had to load the OS off of floppy first, then load your programs from other disks. The A1200 came with 2MB of ram, but I loaded it up with an additional 16MB of RAM, costing a healthy $800. That is just sick.

Back to the subject of hard drives. Here is a rough time line for the consumer hard drive. By "consumer", I mean something that fits in a desktop PC form factor that is in the price range for an average consumer.

1980 5MB ~$1,000.00
1992 1GB ~$1,000.00 (1 gigabyte ~ 1000 megabyte)
2007 1TB ~$300.00 (1 terabyte ~ 1000 gigabyte, or 1 million megabyte)
???? 1PB ???? (1 petabyte ~ 1000 terabyte, or 1 million gigabyte)
???? 1EB ???? (1 exabyte ~ 1000 petabyte, or 1 million terabyte)
???? 1ZB ???? (1 zetabyte ~ 1000 exabyte, or 1 million petabyte)
???? 1YB ???? (1 yottabyte ~ 1000 zetabyte, or 1 million exabyte)

The timeline between 5MB and 1GB drives was 12 years.
The timeline between 1GB and 1TB drives was 15 years.
Notice the price drop!

So let's hear the predictions. When will the first consumer-ready petabyte drive be available, and what will the average cost be? How aboute exabyte? Zetabyte? Yottabyte?

A Yottabyte is a tough one to grasp. That is ONE TRILLION terabytes. Do you think storage space, or personal computing as we know it, will end at some point, long before these outrageous sizes are a reality?

If history is any indication, the petabyte drive should arrive in 12-15 years, and average $300 or less. I think it will much sooner, cut that time down to about 8 years. The $300 price is probably close.

I also think solid-state disk storage will become the norm, seeing hard drive platters die like the video tape did.

iPhone 2.2.1 available fonts

Here is a list of the fonts available to the iPhone as of SDK 2.2.1:


Family: Courier
Font: Courier
Font: Courier-BoldOblique
Font: Courier-Oblique
Font: Courier-Bold
Family: AppleGothic
Font: AppleGothic
Family: Arial
Font: ArialMT
Font: Arial-BoldMT
Font: Arial-BoldItalicMT
Font: Arial-ItalicMT
Family: STHeiti TC
Font: STHeitiTC-Light
Font: STHeitiTC-Medium
Family: Hiragino Kaku Gothic ProN
Font: HiraKakuProN-W6
Font: HiraKakuProN-W3
Family: Courier New
Font: CourierNewPS-BoldMT
Font: CourierNewPS-ItalicMT
Font: CourierNewPS-BoldItalicMT
Font: CourierNewPSMT
Family: Zapfino
Font: Zapfino
Family: Arial Unicode MS
Font: ArialUnicodeMS
Family: STHeiti SC
Font: STHeitiSC-Medium
Font: STHeitiSC-Light
Family: American Typewriter
Font: AmericanTypewriter
Font: AmericanTypewriter-Bold
Family: Helvetica
Font: Helvetica-Oblique
Font: Helvetica-BoldOblique
Font: Helvetica
Font: Helvetica-Bold
Family: Marker Felt
Font: MarkerFelt-Thin
Family: Helvetica Neue
Font: HelveticaNeue
Font: HelveticaNeue-Bold
Family: DB LCD Temp
Font: DBLCDTempBlack
Family: Verdana
Font: Verdana-Bold
Font: Verdana-BoldItalic
Font: Verdana
Font: Verdana-Italic
Family: Times New Roman
Font: TimesNewRomanPSMT
Font: TimesNewRomanPS-BoldMT
Font: TimesNewRomanPS-BoldItalicMT
Font: TimesNewRomanPS-ItalicMT
Family: Georgia
Font: Georgia-Bold
Font: Georgia
Font: Georgia-BoldItalic
Font: Georgia-Italic
Family: STHeiti J
Font: STHeitiJ-Medium
Font: STHeitiJ-Light
Family: Arial Rounded MT Bold
Font: ArialRoundedMTBold
Family: Trebuchet MS
Font: TrebuchetMS-Italic
Font: TrebuchetMS
Font: Trebuchet-BoldItalic
Font: TrebuchetMS-Bold
Family: STHeiti K
Font: STHeitiK-Medium
Font: STHeitiK-Light


Perl Compatible Regular Expressions with Cocoa

If you want Perl Compatible Regular Expressions with Cocoa, Christopher Bess has created ObjPCRE, a library that makes PCRE easy in Cocoa.

However, there isn't much for documentation, so I thought I'd at least show how to get started. Implementation is pretty straight forward. First, you need to add the following files to your XCode project:

libpcre.a
pcre.h
objpcre.h
objpcre.m

You can find the libpcre.a file in the pcre static lib download, and the other three files are in the source file download. I created a new "PCRE" group folder in my XCode project and dropped them all in there.

Now, its just a matter of using it. So first, lets create a one-liner that search/replaces text in a string. We'll search for "string" and replace it with "foobar".

#import "objpcre.h"

NSString *myText = @"This is my string of text.";
NSLog(@"text before: %@", myText);
[[ObjPCRE regexWithPattern:@"string"] replaceAll:&myText replacement:@"foobar"];
NSLog(@"text after: %@", myText);

There you go, your first one-line to search/replace a string of text inline with perl regular expressions. Now this isn't very interesting, as no regular expressions were used. So now, let's try something useful. How about a regular expression that removes all HTML tags from the string. Lets try to think of a regex that will match every HTML tag:

<.*>

Ok that one is pretty basic. It says match <, followed by zero or more of ANY character, followed by >. This could cause a problem because it can match too much, such as multiple html tags along with any text between them. So we'll go with something a bit more restrictive:

<\w+[^>]*>

Now we will only match <, followed by one or more word characters (letter, number, underscore), followed by zero or more characters that are NOT >, followed by >.


We still have a problem though, this will not match closing HTML tags.

</?\w+[^>]*>

There, now we match tags with 0 or 1 "/" after the opening tag.

Notice that backslashes must be escaped inside @"double quotes", so we use two of them in the string.

#import "objpcre.h"

NSString *myText = @"<title>This is my <b>string</b> of <class name="foo">text</class>.</title>";
NSLog(@"text before: %@", myText);
[[ObjPCRE regexWithPattern:@"</?\\w+[^>]*>"] replaceAll:&myText replacement:@""];
NSLog(@"text after: %@", myText);

And now for something a bit trickier. Let's try extracting all words within [brackets] in the text. This is where ObjPCRE could use some more features! But for now, here is how we accomplish this task. First the regular expression that matches the tags:

\[\w+\]

The brackets have special meaning to PCRE, so we have to escape them. This matches [, followed by one or more word characters, followed by ]. But, lets say we want to capture just the text, without the brackets. We put parenthesis around each subpattern we want to capture. These will have no affect on the regex.

\[(\w+)\]

And now we put this into code. Remember to escape backslashes.

NSString *myText = @"This is [some] more [text] to parse.";

ObjPCRE *pcre = [ObjPCRE regexWithPattern:@"\\[(\\w+)\\]"];

int start = 0;
int len = 0;
int offset = 0;
int i = 0;
while([pcre regexMatches:myText options:0 startOffset:offset]) {
for(i=0; i<[pcre matchCount]; i++) {
NSLog(@"match %d: %@",i,[pcre match:myText atMatchIndex:i]);
}
[pcre match:&start length:&len atMatchIndex:0];
offset = start + len;
}

We call regexMatches for each [bracket] pattern it finds. For each of those we loop over the subpatterns and echo them. The first subpattern is the entire match, followed by each parenthesized subpattern (which we have only one.)

Alright, so that's a start! To continue, check all the functions available in objpcre.h, and also see the documentation on PCRE for all the good regex stuff.

Reset a UIScrollView

This has to be the most puzzling thing I've come across in iphone app building thus far. I wanted to "reset" a UIScrollView after pinch zooming and scrolling. It turns out, there is no way to reset the zoom factor on the contentView in a UIScrollView. At least not in the current SDK. You must completely replace the subview of the scroll view to work around it.

I wanted this transition to happen smoothly, so I used some core animation. Here is some working code to get the scroll view to "reset". In my app, I implemented this after a double tap, and after an orientation change.

self.scrollView is the UIScrollView, and self.imageView is the UIImageView subview.


- (void) resetImageZoom {

// animate the transition
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDelegate:self];
[UIView setAnimationDidStopSelector:@selector(resetAnimFinish:finished:context:)];
[UIView setAnimationDuration:0.4];

// reset the scrollview and the current image view
self.scrollView.transform = CGAffineTransformIdentity;
self.scrollView.contentOffset = CGPointZero;
self.imageView.frame = self.scrollView.frame;
self.imageView.center = self.scrollView.center;
self.scrollView.contentSize = self.imageView.frame.size;

[UIView commitAnimations];

}

-(void)resetAnimFinish:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context {

// make a copy of the image view
UIImageView *copy = [[UIImageView alloc] initWithImage:self.imageView.image];
copy.autoresizingMask = self.imageView.autoresizingMask;
copy.contentMode = self.imageView.contentMode;
copy.frame = self.imageView.frame;
copy.center = self.imageView.center;

// replace the current image view with our copy
[self.imageView removeFromSuperview];
self.imageView = copy;
[self.scrollView addSubview:copy];
[copy release];
}

If you wanted, you could extend UIImageView an implement the NSCopying protocol, then just use the copy convenience method. I chose to copy the object a bit more manually here.