I am updating an app to have high-res images to be displayed on the new iPhone 4. My original images (in a UIImageView) were 100 by 100 pixels, so I updated my new images to be 200 by 200 pixels.
I know about the #2x convention, but my images are not stored locally in my project - they are retrieved from the web and being used for both iPhone 4 and other iPhones/iPod touches so they do not include #2x in their name.
Is there anything special I need to display these images properly? Do I need to send down separate versions depending on the device? Or can I send down a high-res version and set some sort of scale?
One issue I think may be causing this is I am building using Base SDK 3.2, which probably has no idea how to handle displays that are higher density than those pre-dating the iPhone 4. I think this may be an issue, because my problem seems rooted in the "point vs pixel" discussion in Apple's docs and the scale factor of an image:
http://developer.apple.com/iphone/library/documentation/iphone/conceptual/iphoneosprogrammingguide/SupportingResolutionIndependence/SupportingResolutionIndependence.html
Thoughts?
Many thanks!
I've had this problem too, the problem related to a clipping mask I was applying to the image. However, I was using 4.0 base SDK, 3.0 deployment target. What I did was check for the -[UIScreen scale] method I'd pass to the mainScreen and see if it was 2.0 (if it infact responded to it). If it was, I knew the scale was 2.0, I'd then call the method that applied the clipping mask with the proper scale. The problem wasn't passing in the data with the right scale, the problem was adjusting the core graphics code to account for the scale; it was applying the clipping mask in one scale, when the image itself was in another scale. If you show us code of what you're doing, I can revise my answer to show you code that will likely help you.
Related
When i create an image for an ImageView to iPhone, iPhone retina, iPad, iPad retina, should i create 4 images ?
For example for a coin image that i use ->
coin.png
coin#2x.png
coinIpad.png
coinIpad#2x.png
Can i create just the most-size image (imageIpad#2x.png) and inside Xcode select Aspect Fit ?
[UIImage imageNamed:#"imageIpad#2x.png"];
Which is the common way to do this?
To answer you question as you asked it: Yes you can just use the highest resolution image only and have it fitted to the size that each device currently needs. You can to that by just initializing the UIImage with the named resouce, as you suggest, and assign that to an UIImageView with an appropriate frame in each device type.
Would I advice doing so? No!
Why?
The naming conventions (~ipad and #2x) make it easy for you as programmer to provide perfectly fitted artworks for each resolution.
You or your designer respectively are in full control over how the artworks will be displayed
It saves memory and cpu and therefore even a bit of battery power.
When it comes to very detailed or small graphics that don't rezise well, then you can consider creating slightly different ones for the lower resolutions that suit better for their current resolution
So if you just want to downsize a high-res image then download something powerful but cheap like gimp and reszise it once yourself (instead of having thouthands of mobile phones do it again and again), save them with poper names and include them in the boundle.
Creating only one image and relying on the device to resize it is:
Inefficient - you're going to be using a lot of resources at runtime that should be busy doing other things
Not the intended way - you should create 2 images (retina and non-retina). If you wish to use another set of images for iPad, you should either check which device you're running on at runtime by using:
[[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad
or by splitting your project into 2 separate targets and adding the 2 sets of images separately to their correct target.
All you need to do is to put coin when you want to call it.
For example:
[UIImage imageNamed:#"coin"];
But when put the images in the resources folder, name it as coin#2x.png for retina image and coin~ipad.png for ipad images.
Xcode will call the appropriate image accordingly.
If you just want to have resizable assets that you can create once and use in different situations - have a look at this UIImage+PDF category that helps you use a PDF, which as a vector format can be scaled to whatever size without loss of quality.
Cacheing has been recently added, which should be a help as well.
since iPhone 4 now has 640X960 resolution i am confused how to build a proper UI for both 320 X 480 and 640 X 960 resolutions.. if i only use images and stuff of 640X960 resolution will it automatically adjust itself for smaller resolution iPhones.. if not what is the best way to differentiate on basis of device resolution??
You make 2 of each image - the first one at normal scale and named the usual "whatever.png". Then you make a second hi-res version of that image at double the scale and name it "whatever#2x.png". Then, iOS will handle the rest. You'll add both of those images to the project, and anywhere in the code that you reference "whatever.png", the system will take care of grabbing and using "whatever#2x.png" when and if appropriate, so you don't have to fuss with much. That's it. Simple.
In Interface Builder, just lay things out like normal using the standard sized graphics. In code as well, just reference images as usual, referring to the standard-sized images. So long as the higher-res counterpart is named with the "#2x.png" appended, everything will just work.
So, just as an example, say you currently have a project with a button image sized 40x100 named "awesomeButton.png". To support the retina resolution, create a new button image sized at 80x200, and name it awesomeButton#2x.png. Import it into your project and iOS takes care of the rest.
According to Apple, the iPhone 4 has a new and better screen resolution:
3.5-inch (diagonal) widescreen Multi-Touch display
960-by-640-pixel resolution at 326 ppi
This little detail affects our apps in a heavy way. Most of the demo apps on the net have one thing in common: They position views in the believe that the screen has a fixed size of 320 x 480 pixels. So what most (if not all) developers do is: they designed everything in such a way, that a touchable area is (for example) 50 x 50 pixels big. Just enough to tap it. Things have been positioned relative to the upper left, to reach a specific position on screen - let's say the center, or somewhere at the bottom.
When we develop high-resolution apps, they probably won't work on older devices. And if they do, they would suffer a lot from 4-times the size of any image, having to scale them down in memory.
According to Supporting High-Resolution Screens In Views, from the Apple docs:
On devices with high-resolution screens, the imageNamed:,
imageWithContentsOfFile:, and
initWithContentsOfFile: methods
automatically looks for a version of
the requested image with the #2x
modifier in its name. It if finds one,
it loads that image instead. If you do
not provide a high-resolution version
of a given image, the image object
still loads a standard-resolution
image (if one exists) and scales it
during drawing.
When it loads an image, a UIImage object automatically sets the size and
scale properties to appropriate values
based on the suffix of the image file.
For standard resolution images, it
sets the scale property to 1.0 and
sets the size of the image to the
image’s pixel dimensions. For images
with the #2x suffix in the filename,
it sets the scale property to 2.0 and
halves the width and height values to
compensate for the scale factor. These
halved values correlate correctly to
the point-based dimensions you need to
use in the logical coordinate space to
render the image.
This is purely speculation, but if the resolution really is 960 x 640 - that's exactly twice as high a resolution as the current version. It would be trivially simple for the iPhone to check the apps build target and detect a legacy version of the app and simply scale it by 2. You'd never notice the difference.
Engadget's reporting of the keynote included the following transcript from Steve Jobs
...It makes it so your apps run
automatically on this, but it renders
your text and controls in the higher
resolution. Your apps look even
better, but if you do a little bit of
work, then they will look stunning. So
we suggest that you do that
So I infer from that, if you use existing APIs your app will get scaled up. If you take advantage of new iOS4 APIs, you can get all groovy with the new pixels.
It sounds like the display will be ok but I'm concerned about the logic in my game. Will touchesBegan positions return points in the new resolution? The screen bounds will be different, these types of things could potentially be problems for me.
Scaling to a double resolution for display purpose is straight forward, but will this scalling apply to all api's that input/output a screen coordinate? If not things are going to break aren't they?
Fair enough if it's been handled extensively throughout the framework.. I would imagine there are a lot of potential api's this effects.
For people who are coming to this thread looking for a solution to a mobile web interface, check out this post on the Webkit blog: http://webkit.org/blog/55/high-dpi-web-sites/
It seems that Webkit has solved this problem four years ago.
Yes it is true.
According to WWDC it appears that apple has build it some form of automatic conversion so that the resolution for applications will not be completely off. Think up-convert for dvd to HDTV's.
My guess would be that apple knows what most of the standards developers have been using and will already be using these for an immediate conversion. Of course if you are programming an application to take advantage of the new resolution it will look much nicer than whatever the result of apples auto-conversion is.
All of your labels and system buttons will be at 326dpi but your images will still be pixel doubled until you add the hi-res resources. I am currently updating my apps. If you build and run on the iPhone 4 sim then it is presented at 50%, go to Window > Scale > 100% to see the real difference! Labels are smooth, my images look shocking!
I've run into the issue of using a UIBarButtonItem with a custom color. Everything out on the 'net seems to indicate that the only way around this lack of official API support revolves around the use of images. This is all fine and dandy when developing for pre-iOS 4 devices, except when using the new iPhone 4. Creating an image for iPad and pre-iOS 4 devices is straightforward enough, but the images developed for those devices look absolutely horrid on iPhone 4. I suspect that this problem will be exacerbated further with the introduction of next generation devices.
Consider the example below. Notice how the default colored button is nice and smooth, but the iPhone 3GS image looks terrible. It does not seem very scalable (pun intended) to have to include multiple images for different resolution devices.
In the absence of an official API for changing the color of a UIBarButtonItem, what strategies are out there for creating images that scale well against differing resolution devices? This problem is hardly unique to UIBarButtonItems, how is the community adapting to other UI elements that are bitmapped? Is there a better solution for this particular case than using an image (such as using Quartz to draw it)?
If at all possible, please offer concrete code examples.
You can list any image as Image#2x.png along with Image.png and the system will select the appropriate image at runtime.
If you look at the source for Three20 you can see how they draw custom buttons and shapes that will scale well, regardless of resolution.
Give Opacity (for Mac) a try. Draw your button in it with vector elements and effects, and it'll spit out the necessary Quartz code to reproduce it, drawing natively in your iOS application. You get Retina (#2x) support automatically.
Been over a year since I posted this question, but ran into a use case where I wanted to be able to do this, so instead of having to draw or otherwise create the buttons, I decided to write an open source application to create them. This application uses private APIs to change the colors of the UIBarButtonItem objects and then uses a graphics context to save them to a determined location on your computer's file system. This way you can have pixel perfect UIBarButtonItem images to use in your UIToolbars.
The app creates both the standard and #2x resolution images.
UIBarButtonItem-Generator # GitHub
Any vector drawing app may work, but I would also consider povray, which allows you to create in a C-like scripting 3D language, then export any pixel size you choose.
http://povray.org
I have the same problem with navigation bar so solve as the following:
first i subclass my navigation bar
inside this class
- (void)drawRect:(CGRect)rect
{
UIImage *image=[UIImage imageNamed:#"MyImage.png"];
self.frame=CGRectMake(0, 0, image.size.width, image.size.height);
self.backgroundImage =image;
}
finally save the same image with different resolution With #2x at the end
I have a button with an image set through interface builder. The original image is SearchImage.png and the high rez version is SearchImage#2x.png. I'm absolutely sure that no typos were made, and the higher resolution image is indeed exactly twice the size (ie twice as tall, twice as wide) as the lower resolution image, yet the office's iPhone4 still only loads the low resolution image.
Does anyone have any ideas what the problem might be?
I have read all the relevant Apple documentation.
Thanks!
Tristan
Just assign the image property "SearchImage.png" and include both SearchImage.png and SearchImage#2x.png in your main bundle and it will load the correct image.
See https://devforums.apple.com/message/233916#233916.