I have a UIScrollView with paging enabled. All the images were loaded at the start and added to the UIImageViews, but I had a memory-issue as it were more images, so I decided to load the after next image while scrolling if the image isn't set yet. If i get a memory warning, I remove all images except of the current.
The problem is, that the scrollview hangs for a few milliseconds if I scroll.
I'm using
UIImage *image = [UIImage imageNamed:#"path/to/image.png"];
to load the images. If I use the method imageWithContentsOfFile, it cost alot more time.
Is there a way to show a pixelated image like in the default Photoapp until it's fully loaded?
Thanks for your answers in advance.
[UIImage imageNamed:]
caches images for you, so that's why it's better than imageWithContentsOfFile. Since these images are displayed in a table cell, presumably they don't need to be that large. What are the images dimensions on the file system? If you just put the UIImage in a UIImageView and depend on that for scaling, my guess is the scaling happens while you scroll. Can you create thumbnails for each image on the file system and use those?
Related
When using the following code:
self.view.backgroundColor = [[UIColor alloc] initWithPatternImage:[UIImage imageNamed:#"texture1.png"]];
The texture background of my view gets set just fine. But I can see that the images are not scaled properly for a retina display, they seem more pixelated, rather than rich in texture and color as they should be. I have had this issue with other images too, when trying to make an image the size of the iphone 5 screen fade away, only a part of it would be seen, and the rest would be cut off, even though the resolution is fine. Any idea what I am missing here?
EDIT: Does it have to do with the default dpi of the images that I am using?
EDIT #2: Here is a screenshot:
On a side note, does anyone know if good background texture sources besides http://subtlepatterns.com/?
EDIT #3: Here is a good example of me attempting to use the ios-linen pattern
firstly remove .png from image name if you are use #2x image
self.view.backgroundColor = [[UIColor alloc] initWithPatternImage:[UIImage imageNamed:#"texture1"]];
Please check the image height and width for retain display ..
By Apple 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. If it 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.
Instead of using initWithPatternImage you should add a UIImageView to the UIView . This is better because :-
The UIImageView will contain the image according to its specific width and height.
Also, the initWithPatternImage method consumes MORE MEMORY than the UIImageView.
I would prefer to use a UIImageView rather than the
initWithPatternImage:[UIImage imageNamed:#"texture1.png"]
If the image is still not clear you can add the #2x image to the UIImageView and you will see the clarity is more.
I'm loading a 5MP image into an UIImageView calling self.imagecontainer.image = myUIImage. myUIImage is an image coming from the camera of the iPhone.
This takes some time before the image can be seen on screen, and even if I can reduce this time, I need to start a process when the image is really displayed on the screen.
How may I know that the image is loaded and displayed, and not just still being processed by the UIImageView ?
Well... first thing is you shouldn't be setting a 5MP image in an imageView. An imageView is meant for on screen display only and even though it scales the image you set for display purposes the original is retained so your memory footprint goes way up. If you do this at best you will have a poor performing app that deals with lots of memory warnings. At worst, you'll crash often.
So, you should resize your image to the smallest size that meets your onscreen display needs and then set that image within your imageView. This is my favorite blog post on how to resize images: http://vocaro.com/trevor/blog/2009/10/12/resize-a-uiimage-the-right-way.
Now, to your question. You can't know for sure when the image is displayed but it will happen so quickly once you scaled you can just assume it is displayed as soon as you set it. So do your scaling on a background thread. When the scaling is done, send a message to the main thread to set the scaled image in the imageView and then do whatever you want.
i want to display image in UIImageView which is on the UIScrollView and using Touch Event the image should change from Right-to-Left and Left-to-Right also.The images are the result of NSXml parsing so what should i do please help me in this task.what should i do and if possible then show me with some example.Thanks in Advance.....
Depends on how you obtain the images.
If you get them as URLs, you need to download the actual images. There are examples of doing this.
If you get them as NSData (from downloading them or such), you just have to init a UIImage with the data, e.g. [UIImage imageWithData:] or [[UIImage alloc] initWithData:].
Then you just do what everyone else does when adding an image to a scroll view. There are hundreds of examples. In short, add the image to a UIImageView then add that view to the scroll view using addSubview:.
I have a custom UIImageView class which I use to handle multi-touch events on the UIImageView. When the user touch begins, I want to increase the UIImageView's frame but keep the UIImage size fixed.
I tried changing the UIImageView's frame and then calling the drawInRect: method of UIImage to keep the UIImage's size fixed. But this is not working.
The contentMode for the UIImageView is set as ScaleAspectFit and as soon as I increase the frame size of the UIImageView, the UIImage size also increases (and is not affected by the drawInRect:)
Can someone please tell me how I can achieve this?
Thanks.
Adding more details
What I am trying to do is this
Place a UIImageView on the screen with the size same as the size of the image
When the user selects the image, anywhere he touches, the image edits as if the user is doing multi-touch with the image
If I increase the size of the imageview to detect touches any where, the image size also increases... Hope that makes things clearer!
Thanks
There may well be other ways to do it, but I think the UIImageView is doing what it's intended to do here.
What do you want the area of the view not covered by the image to look like? Be transparent? Have a solid colour?
Why do you want to do this? Is it to capture touch events from a wider area than that under the image itself?
If you have a good reason for needing to do this I would create a new view, probably just a plain UIView (with background set to transparent colour), and add the UIImageView to that. Make the plain view the one you resize.
I haven't specifically tried this, but I think it would work:
imageView.contentMode = UIViewContentModeCenter;
I have defined an UIImageView in my nib. After the app launches, I display an image in that UIImageView. Maybe I am on the wrong way, but what I want to do is the following:
The image which I load into the view is bigger than the view itself. I want that it is displayed in original size with hidden overlay. Then I want to slowly move that image inside that view in random directions.
Maybe you know html div containers with background images. there, you can set a position of that background image and change that position with JavaScript. I need something similar on iPhone.
Maybe an UIImageView is not the right thing for that? Or must I set the UIImageView to the full size of that image and then move the UIImageView around slowly? Could it be bigger than the iPhone's screen?
You need to crop the image. See Lounges' answer to this question.
This is the gist of my answer to pretty much the same question:
There isn't a simple class method to do this, but there is a function that you can use to get the desired results: CGImageCreateWithImageInRect(CGImageRef, CGRect) will help you out.
Here's a short example using it:
CGImageRef imageRef = CGImageCreateWithImageInRect([largeImage CGImage], cropRect);
[UIImageView setImage:[UIImage imageWithCGImage:imageRef]];
CGImageRelease(imageRef);