I have 3 short questions, very related:
How do i detect if the user is using a retina device?
I want to save an image inside my app in documents, if i detect that they're using a retina display phone and save the image ending in #2x.jpg will it work as it does with imported images, where it'll automatically go for that one instead on a retina device?
If i were to reference an image which didn't exist, but a #2x.jpg version existed, would it go to that by default?
Use [UIScreen mainScreen].scale, it's 2.f when it's a retina screen.
I'm not sure, but I think it'll automatically detect #2x-versions here too (as long as you use UIImage to load them).
If it's a retina screen, it'll look to the #2x-version first, if it doesn't exist, it'll fallback to the default-version. If that version doesn't exist, it'll return nil. A non retina screen however, will never look to the #2x-version.
You call it a x2.jpg-file, however, it isn't:
Your default file is something like background.png.
Then your retina file should be like background#2x.png.
You load the image using UIImage *image = [UIImage imageNamed:#"background.png"];.
In most situations you don't need to know if it's a retina screen, iOS will handle this.
Related
I would like to have images for my UIButtons, screen background etc in my iPhone app.
Will it work for both Retina display and normal display if I have
ButtonImage.png and ButtonImage#2x.png
Background.png and Background#2x.png
OR, should I do any extra coding so that it works for both displays?
ButtonImage.png is looking awkward on Retina Simulator. So, I should have a higher resolution image. So... please help me.
Chandu
UIImage's imageNamed: method automatically looks up the #2x images on the retina device if they're available; no additional coding is required.
If you’re putting the image in your user interface in a .xib file, or if you use the +imageNamed: class method for UIImage, then the #2x suffix is sufficient to load Retina images.
you have nothing to do, ios do the job to choose the right one
Short Answer: Yes, that is the right way to do what you want. UIImage will figure it all out for you.
However, don't forget that you can't just copy and rename a given image (say, Background.png). You need to get an image that is the same as Background.png, but four times the resolution (that's the same as double the width and double the height). Then, you can name that Background#2x.png and everything'll be peachy keen.
Here you have to use the simple image and it will work for both, Normal display as well as retina display. You just specify simple images with ButtonImage.png & Background.png in the resource bundle and retina images ButtonImage#2x.png Background#2x.png in the resource bundle.
Now you just need to specify the simple images in the code and retina image will automatically taken when running on the device with retina screen resolution i.e. iPhone 4 and later.
backgroundImageView.image = [UIImage imageNamed:#"Background.png"];
The same code will work and when iPhone 4 with retina display it will consider the image Background#2x.png from resource bundle automatically.
Let me know if you have any other question.
That's the right thing i mean whatever you are using or describing the way,but second thing
you need to do is that allocating the position for buttons.
If you will allocating position as a constant or fix by declaring x,y coordinate then it might not work,so try to allocate position of button in dynamic way so that it will take position once retina will call it.
Thanks
I have icons inside my application for uibutton & on uitable cell. Lets say I have image named "sampleImage.png". Can my app use the image named "sampleImage#2x.png iphone with retina display automatically provide it is in my app bundle ?
If yes how can write code for it because I have code like
cell.imageview.image = [UIImage named:#"sampleImage.png"];
Does it work even if I hardcoded the image name?
Any kind of help is appreciated.Thanks
Yes, UIImage will automatically use the #2x version of an image on a retina display.
Searching for an answer of your question I came across this: what is the code to detect whether ios app running in iPhone, iPhone Retina display, or iPad?
One of the answers mentions this:
There's often no need to determine directly whether you're on a retina display because UIImage handles that automatically when you use imageNamed and append "#2x" to your high resolution image file names (see Supporting High-Resolution Screens in the Drawing and Printing Guide for iOS).
I have an iPhone Xcode project that currently only contains images for retina display (twice the size as normal and with a #2x.png suffix). When I run the app on the iPhone Simulator (non retina) the images are still being displayed. Does this mean I don't need to worry about including two sets of images: retina and non-retina?
This all seems a bit odd. I would assume that no images would appear on a non retina device if there are no non-#2x files included.
Note: I have not tested my app on a non retina device. Just the simulator.
I'm pretty sure that iOS will just use the #2x and scale it down if you don't have a non-retina graphic. Although that's sub-optimal since you're letting iOS do the scaling at runtime which will be slower than including the non-retina graphic and also iOS might not do as good a job as scaling as your graphics editor of choice.
Even if it works, it's not good practice, and if you have a media heavy app definitely it would impact performance and battery life and memory foot print and ....
By the way, is it just that you don't have the 1x graphics available to you or you are concerned about your apps (download size) or ...
If you are assigning the images in Interface Builder, and you set the image property on a UIImageView to image#2x.png, for example, iOS will not know that it's a high resolution "2x" image. In fact, on a retina display, iOS will look for an image named image#2x#2x.png. Since it won't find it, it will set the scale factor of the image to 1.0.
The contentMode property (just "mode" in XCode) will decide if any scaling of the image occurs to fit the constraints of the UIImageView. You may wish to set the mode to "Aspect Fit" to get the high resolution image to scale as needed for both retina and non-retina displays. In general, the image will display as seen in Interface Builder.
If you are using UIImage's imageNamed or similar function to load the image, and just specify image (where "image.png" doesn't exist, but "image#2x.png" does), then iOS will actually find the image on a non-retina display, though the scale factor will be 1.0. As previously, you'll need to scale it to fit your view. The image will work normally on a retina device, and the scale factor will be set to 2.0, since iOS looks for a "2x" image first, and it doesn't matter if the other file exists or not.
This is from Apple's documentation on imageNamed:
On a device running iOS 4 or later, the behavior is identical if the
device’s screen has a scale of 1.0. If the screen has a scale of 2.0,
this method first searches for an image file with the same filename
with an #2x suffix appended to it. For example, if the file’s name is
button, it first searches for button#2x. If it finds a 2x, it loads
that image and sets the scale property of the returned UIImage object
to 2.0. Otherwise, it loads the unmodified filename and sets the scale
property to 1.0. See iOS App Programming Guide for more information on
supporting images with different scale factors.
If at all possible, you really should include both retina and non-retina images. Using higher-resolution images than necessary negatively affects memory and performance.
I'd like to design a background image for my app. The image should fill the iPhone screen.
What image size that will work for 3G and 4G?
A) 320 x 480.
B) 640 x 960.
I prefer to use B as it will have more quality, will 3G resize the image to fit?
Thanks for any help.
Simply author both sizes and save the hi-res with a #2x suffix in the filename (like background.png and background#2x.png). iPhone 4 will use the hi-res image, older devices will stick to the ordinary one. See the docs for +[UIImage imageNamed::
This method looks in the system caches
for an image object with the specified
name and returns that object if it
exists. If a matching image object is
not already in the cache, this method
loads the image data from the
specified file, caches it, and then
returns the resulting object.
On a device running iOS 4 or later,
the behavior is identical if the
device’s screen has a scale of 1.0. If
the screen has a scale of 2.0, this
method first searches for an image
file with the same filename with an
#2x suffix appended to it. For
example, if the file’s name is button,
it first searches for button#2x. If it
finds a 2x, it loads that image and
sets the scale property of the
returned UIImage object to 2.0.
Otherwise, it loads the unmodified
filename and sets the scale property
to 1.0. See iOS Application
Programming Guide for more information
on supporting images with different
scale factors.
Also read the appropriate part of iOS Application Programming Guide.
Although it is trivial to resize the image to the proper size, you should prepare both 320×480 and 640×960 (and probably you need a 1024×768 for iPad too). In this way the system can choose the best image for that model.
Basically, you create a 320×480 background.png for the older models, and a 640×960 background#2x.png for retina display. Then load the image with
UIImage* backgroundImage = [UIImage imageNamed:#"background.png"];
in this way, the system will choose the best resolution automatically.
I've installed my iPhone app on an iPad. When I tap this "2x" button, the app gets scaled up, but it doesn't use my retina display graphics. Isn't that somewhat stupid? I am sure I did something wrong!
What must I set in the info.plist or elsewhere that the iPad will use my retina display graphics when the app is watched in 2x mode?
No, it literally just scales up the screen. It may be a bit lame but that's by design. Note that even the text is pixel-doubled.
If you want to make better use of the screen you have to make a "Universal" app.
If you use a hi-res image (not called #2x) in your app, then size the UIImageView half the size of the image it will appear crisp on the iPhone, retina, and iPad scaled up.
Please make sure your retina image naming convention is correct.
For retina image naming convention should be #2x.Suppose if your regular image name is like
icon.png then for retina it should be icon#2x.png.