I am having difficulties with retina images.
The screenshot below shows the UICollectionView with a UIImageView contained within each UICollectionViewCell.
Within the app I have a large image 512x512 pixels called travel.png.
The green circle shows what is displayed on the app when I name this file: travel.png. The blue circle shows what I see when I update the image name to be travel#2x.png (i.e. retina naming).
I was hoping due to the large size of the image (512x512) that simply adding the #2x suffix would be enough to convert it to twice the definition (i.e. retina) but as you can see from the two screenshots, both version images show as non-retina.
How can I update the image so that it will display in retina?
travel.png:
travel#2x.png:
* Updated *
Following request in comments below:
I load this image by calling the following function:
// Note - when this method is called: contentMode is set to .scaleAspectFit & imageName is "travel"
public func setImageName(imageName: String, contentMode: ContentMode) {
self.contentMode = contentMode
if let image = UIImage(named: imageName) {
self.image = image
}
}
Here is how the image appears in Xcode before the app renders it (as you can see it is high enough definition):
The reason why you see the low quality image is anti-aliasing. When you provide images bigger then an actual frame of UIImageView (scaleAspectFit mode) the system will automatically downscale them. During scaling some anti-aliasing effects can be added at curve shapes. To avoid the effect you should provide the exact image size you want to display on the screen.
To detect if UIImageView autoscale the image you can switch on Debug->Color Misaligned Images at Simulator menu:
Now all scaled images will highlight at simulator with yellow color. Each highlighted image may have anti-aliasing artifacts and affect CPU usage for scaling algorithms:
To resolve the issue you should use exact sizes. So the system will use them directly without any additional calculations. For example, if your button have 80x80px size you should add three images to assert catalog with following sizes and dpi: 80x80px (72 dpi), 160x160px (144 dpi) and 240x240px (216 dpi):
Now the image will be drawn at the screen without downscaling with much better visual quality:
If your intention is to have just one image for all the sizes, I would suggest it having under Assets.xcassets. It is easy to create the folder structures and manage media assets here.
Steps
On clicking + icon, you will displayed a list of actions. Choose to create a New folder.
Choosing the new folder that is created, click on the + icon again and click on New Image Set.
Choose the imageset. And choose the attributes inspector.
Select Single Scale, under Scales.
Drag and drop the image.
Rename the image name and folder names as you wish.
Now you can use this image using the image name for all the screen sizes.
TL;DR;
Change the view layer's minificationFilter to .trilinear
imageView.layer.minificationFilter = .trilinear
as illustrated by the device screenshot below
As Anton's answer correctly pointed out, the aliasing effet you observe is caused by the large difference in dimensions between the source image and the image view it's displayed in. Adding the #2x suffix won't change anything if you do not change the dimensions of the source image itself.
That said there is an easy way to improve the situation without resizing the original image: CALayer offers some control over the method used by the graphics back-end to resize images : minificationFilter and magnificationFilter. The first one is relevant in your case since the image size is being reduced. The default value is CALayerContentsFilter.linear, just switch to .trilinear for a much better result (more info on those wikipedia pages). This will require more GPU power (thus battery), especially if you apply it on many images.
You should really consider resizing the images before displaying them, either statically or at run-time (and maybe cache the resized versions). In addition to the bad visual quality, using such large images in quantities in your UI will decrease performance and waste lots of memory, leading to potentially other issues.
I have fixed, #DarshanKunjadiya issue.
Make sure (if you are already using assets):
Make sure images are not un-assigned
Now use images in storyboard or code without extensions. (e.g. "image" NOT "image.png")
If you are not using images from assets, move them to assets.
Demo Projects
Hope it helps.
Let me know of your feedback.
I think images without the #2x and #3x are rendered for devices with low resolutions (like the iphone 4 an 3G).
The solution I think is to always use the .xcassets file or to add the #2x or #3X in the names of your images.
In iOS, content is placed on the screen based on the iOS coordinate system. for displaying an image on a standard resolution system having 1:1 pixel density we should supply image at #1x resolution. for higher resolution displays the pixel density will be a scale factor of 2.0, 3.0 which refers in the iOS system as #2x and #3x respectively. That is high-resolution displays demands images with higher density.
For example, if you want to display an image of size 128x128 in standard resolution. You have to supply the #2x and #3x size image of the same. ie., 256x256 at #2x version and 384x384 image at #3x version.
In the following screenshot, I have supplied an image of size 256x256 for 2x version to display a 128x128 pixel image in iPhone 6s. iPhone 6s render images at #2x size. Using the three version of images such as 1x, 2x and 3x with asset catalogue will resolve your issues. So the iPhone will automatically render the correct sized image automatically with the screen resolution.
I have a very simple requirement here but I'm looking for a solution for a while. I want to take a profile picture form the camera roll or camera and display it in two different image views (different sizes). I don't want any of these images stretched or miss any part of the image. If I use aspect to fit, top side of image is cut from smaller image view and some parts missing on the bigger image view. If I set it as scale to fit, it will get stretched!
I'm not sure how some mobile apps work. Do they save different image sizes in their server or they change the size of the image. I saw many posts how to change image size without changing aspect ratio. But I don't think it is possible to avoid stretched effects. I used some of those code to change size of image, it gets stretched all the time.
Is there any way to save the image from camera roll one time with size of 140*200 and one time 160*200? So I can use 140*200 for image views that size. But what if I have different devices and different sizes.
I have users uploading images using filepicker, but I want them to have to upload an image of a certain size (and crop if the image is too big). I could cut it myself, but then it won't look good. Ideally, the user would crop it themselves.
I've tried this page: https://www.filepicker.com/documentation/file-ingestion/widgets/pick?v=v2 and I've tried various options but nothing seems to work quite well.
data-fp-image-min doesn't prevent users from uploading smaller images. data-fp-crop-force along with data-fp-crop-max and data-fp-crop-min doesn't do the trick either.
I'm open to using other image uploading libraries, but I like using filepicker. Seems like this is something other people would have run into.
I'm using rails btw.
From the docs:
data-fp-image-min - Images smaller than the specified dimensions will be upscaled to the minimum size.
So it doesn't really prevent users from uploading smaller images.
data-fp-crop-max and data-fp-crop-min specifies the maximum and minimum dimensions of the crop area so it won't give you specific dimensions.
I would recommend you to:
Set data-fp-crop-ratio - Specify the crop area height to width ratio. User will be able to adjust the crop area for each photo with desired ratio.
Set data-fp-crop-force="true" - User could not skip cropping image.
Then resize image to specific height or width.
This will result, you will always get the image with the desired dimensions.
Example for 150 x 200 image output:
Html widget:
<input type="filepicker"
data-fp-crop-ratio="3/4"
data-fp-crop-force="true"
mimetype="image/*"
onchange="window.upload(event)"
data-fp-apikey="APUGwDkkSvqNr9Y3KD4tAz" />
Javascript:
window.upload = function(event){
console.log(JSON.stringify(event.fpfile));
var listElem = document.createElement("li");
var image = document.createElement("img");
/*
set w=150 (width) conversion option
so all images would be 150x200
and crop_first option to make sure the image is cropped
before any other conversion parameters are executed.
*/
image.setAttribute('src', event.fpfile.url + '&w=150&crop_first=true');
listElem.appendChild(image);
document.getElementById('results').appendChild(listElem);
};
Here is working solution: http://jsfiddle.net/krystiangw/9o9ebddL/
I am displaying image thumbnails from urls(which are in json file) into custom cells of a tableview.
The images loaded from url are not showing up properly- they are of a resolution much higher than need and some are of much lower resolution.
How do I manipulate these images so that they are scaled properly as per each screen(retina as well as normal) in iphone?
How do I scale and resize the thumbnail images from url?
Unless you care about other issues like memory or disk usage (for some caching) for the images, you don't have to resize them.
You can use UIViewContentModeScaleAspectFit as contentMode for an UIImageView and just set an image for the image view. It would be sufficient for you.
I'm using Nimbus to display a photo album with scrubber and zoomable image view. I use network images, and display a thumbnail until the final image is loaded. NIPhotoAlbumScrollView provides the method didLoadPhoto:atIndex:photoSize: to accomplish exactly that.
From the source code comments, the NIPhotoScrollView should support that "image crisping effect" - showing thumbnail and when full-size image is loaded, sharpen the image without loosing the zoom state.
This feature seems broken though. When the thumbnail is loaded, it is displayed in its 1:1 pixel size, which is very small on screen. When the full-size image is loaded, it is also loaded in its 1:1 pixel size (if smaller than the available view size), which makes the image visually jump bigger.
Any idea on how to fix that issue?
Note that I tried both with a full sized image with dimensions bigger or smaller than the size of the NIToolbarPhotoViewController on screen.
you may already be doing this, but one thing to make certain:
where you implement photoAlbumScrollView:photoAtIndex:photoSize:isLoading:originalPhotoDimensions: for protocol NIPhotoAlbumScrollViewDataSource, you must do the following, as mentioned in these comments in the source:
* If you have a thumbnail in memory but not the full-size image yet, then you should return
* the thumbnail, set isLoading to YES, and set photoSize to NIPhotoScrollViewPhotoSizeThumbnail.