For my iPhone Web App, since the 3G network is very slow, it cannot upload a large photo. Thus, I want to reduce the photo size before I upload it into a server. I tried to use CANVAS HTML 5, which works in Android but not in iOS 7 or 8.
Are there any other methods that I can use to reduce the photo size before upload?
You can use UIImageJPEGRepresentation or UIImagePNGRepresentation to compress the photo.
compressionQuality
The quality of the resulting JPEG image, expressed as a value from 0.0 to 1.0. The value 0.0 represents the maximum compression (or lowest quality) while the value 1.0 represents the least compression (or best quality).
See more info: https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIKitFunctionReference/
Related
In my application, I'm using YPImagepicker for selecting images from library and camera. I want to know image size in MB after selecting the pictures or capturing a photo. Task is to convert the images into data and send to backend via REST API. As of now we are limiting images into 5. So I want to see the size of every images if it is more than 1 Mb need to compress into 1mb.
let imgData = NSData(data: image.jpegData(compressionQuality: 1)!)
var imageSize: Int = imgData.count
print("actual size of image in KB: %f ", Double(imageSize) / 1024.0 / 1024.0)
the above sample I have used to check the size of the image but I'm not seeing the correct file size. For eg, I'm capturing one photo through app and it is getting saved in album when I check the image size it shows 3.4 MB in photo detail but in code I'm not getting the same size. What is best way to achieve this?
Apple doesn’t use JPEG for storing images in your iOS library. They use a proprietary file format with its own lossy compression.
The two file formats will yield different file sizes.
When you load an image from the user’s image library and convert it to JPEG data, it gets re-compressed using JPEG compression with the image quality value you specify. A compressionQuality value of 1.0 will create an image file with the best image quality but the largest file size. That is why your results are bigger than the files from the user’s image library. Try a lower compressionQuality value.
There is one very interesting issue I face at the moment in my iOS application.
The image size got increased by the random number of percentage.
What I have observed is as below
When I choose the same image from the photo library and try to send the image by converting it to data, though the multipart form data API.
The image size also got increased in multiple times of the original image size.
I use the below code to convert the image into data bytes
img.jpegData(compressionQuality: 1.0)
The data length is around 90 MB.
The original image is available here.
Does anyone know where is the issue and how to resolve it?
I have image file in my photos app of iphone.
I have taken it to my macbook, via airdrop and checked size of the image = 1.9 MB
I saved the same image to Files app of iphone and checked the image size there = 1.9 MB
I have taken same image into my app viaUIImagePickerController,
Used UIImagePNGRepresentation and printed the data count/byte count = 15.8 MB
Used UIImageJPEGRepresentation with compressionRatio 1.0 and printed the data count/byte count = 5.4 MB
Used UIImagePNGRepresentation and saved it to local(DocumentsDirectory) and checked the file size = 15.8 MB
Used UIImageJPEGRepresentation with compressionRatio 1.0 and saved it to local(DocumentsDirectory) and checked the file size = 5.4 MB
Now, My question is that, why UIImagePNGRepresentation OR UIImageJPEGRepresentation increases file size to that much large?. I even uploaded this image to my server and obviously getting this larger image sizes. I wanted to upload given image to my server with the original quality, but i dont want this much large sized image(as its actual size on device is totally different), is there any other way by which we can prevent original image size and quality both?.
Let's take this example from WWDC 2018 session - 416_ios_memory_deep_dive. If you have 590kb file size image, the dimension of image is 2048 pixels x 1536 pixels. SO the total memory of this image is 10MB (2048 pixels x 1536 pixels x 4 bytes per pixel) For more details you can take a look at this video. https://developer.apple.com/videos/play/wwdc2018/416/
As title states and as searching on google can give, on iOS there is a limit for what the devices can handle for jpeg images.
As per Apple docs (Know iOS Resource Limits):
Because of the memory available on iOS, there are limits on the number
of resources it can process:
The maximum size for decoded GIF, PNG, and TIFF images is 3 megapixels
for devices with less than 256 MB RAM and 5 megapixels for devices
with greater or equal than 256 MB RAM. That is, ensure that width *
height ≤ 3 * 1024 * 1024 for devices with less than 256 MB RAM. Note
that the decoded size is far larger than the encoded size of an image.
The maximum decoded image size for JPEG is 32MP megapixels using
subsampling. JPEG images can be up to 32 megapixels due to
subsampling, which allows JPEG images to decode to a size that has one
sixteenth the number of pixels. JPEG images larger than 2 megapixels
are subsampled—that is, decoded to a reduced size. JPEG subsampling
allows the user to view images from the latest digital cameras.
I added the enfasis on the point that's bugging me mostly. I'm trying to display a fairly big image, but still largely in the above 32MP mentioned limit, specifically its a 3995px * 2138px for a total of 8.5MP and 396kb weight (jpeg quality/compression set to 25 via PS).
Still whenever I call for that image as ex. source of an <img> tag, nothing is displayed on any iOS device I've been able to test, on emulators and couple real devices (iphone4, ipad2, 3, mini...).
Is there anything I'am missing blatantly or maybe I've not understand from the docs above?
What can I do apart replace it with a reduced file size? If forced to replace it, what is the highest width I can reach without breaking? How can I ensure iOS honor the 32MP limit mentioned?
I'm speaking in a website perspective, not a native app on the device.
It doesn't fix your current problem but if you look at image handling in IOS8 there are no longer any image size limits (CoreImage can automatically tile) - perhaps you could target that?
You can split up images and tile them.I routinely display images 180,000 x 120,000 pixels on IOS devices by chopping them up and using a CATiledLayer.
I want to display a page containing about 6000 tiny image thumbnails (40x40 each). To avoid having to make 6000 HTTP requests, I am exploring CSS sprites, i.e. concatenating all these thumbnails into one long strip and using CSS to crop the required images out. Unfortunately, I have discovered that JPEG files cannot be larger than 65500 pixels in any one dimension. Wary of further limits in the web stack, I am wondering: are any of the following unable to cope with an image with dimensions of 40x240000?
Internet Explorer
Opera
WebKit
Any CSS spec
Any HTML spec
The PNG spec
Edit: the purpose of this is simply to display an entire image collection at once, requiring that the user at most has to scroll. I want the "micro-thumbnails" to flow into an existing CSS layout, so I can't just use a big rectangular image. I don't want the user to have to click through multiple pages to see everything. The total number of pixels is not that great - only twice what would fit on a 2560x1600 display. The total file size of all the micro-thumbnails is only a couple of megabytes. Assuming every image is manipulated uncompressed in the browser's memory, taking 8 bytes of storage per pixel (RGBA plus 100% overhead fudge factor), we are talking RAM usage in the low hundreds of megabytes; not unreasonable for a specialized application in the year 2010. The only unreasonable thing is the volume of HTTP requests that would be generated if all micro-thumbnails were sent individually.
Well, Safari/iOS lists these limits:
The maximum size for decoded GIF, PNG, and TIFF images is 3 megapixels.
That is, ensure that width * height ≤ 3 * 1024 * 1024. Note that the decoded size is far larger than the encoded size of an image.
The maximum decoded image size for JPEG is 32 megapixels using subsampling.
JPEG images can be up to 32 megapixels due to subsampling, which allows JPEG images to decode to a size that has one sixteenth the number of pixels. JPEG images larger than 2 megapixels are subsampled—that is, decoded to a reduced size. JPEG subsampling allows the user to view images from the latest digital cameras.
Individual resource files must be less than 10 MB.
This limit applies to HTML, CSS, JavaScript, or nonstreamed media.
http://developer.apple.com/library/safari/#documentation/AppleApplications/Reference/SafariWebContent/CreatingContentforSafarioniPhone/CreatingContentforSafarioniPhone.html
Based on your update, I'd still really recommend not using this approach. Don't you think there's a reason that Google's image search doesn't work like this?
As such, I'd recommend simply loading images as required via Ajax. (i.e.: When the user scrolls below the currently visible set of images.) Whilst this will use more connections, it'll mean that you can have sensibly sized thumbnails and as a general approach is much more manageable than having to re-generate pre-generated thumbnail image "sheets" on the back-end when a new image is added, etc.