I have an application that let's users view images. The user decides what images to use, so the size can range from 10x10 to 10000000x10000000 (I am exeggerating). All is well up to a certain size, when the image is bigger than the iPhone's memory. Quite understandably.
But how do I fix it? Is there a way to load only a portion of the image (I'm using an CATiledLayer, so I could load/release tile by tile).
Thanks in advance!
Unless you have an uncompressed image format it would be very hard to load the image in patches, you will have to provide the patches that the user would load, determine what portion of the image to show, and load the correct patches. There is an example for this "ScrollViewSuite" that demonstrate that technique. But this technique does require a preprocessing step.
Related
I want to make a kind of slideshow based on scrolling the webpage.
My problem is that I have an image width of 78720x1015px in png-format.
The width of the image is determined by one single image of 1920px which is 41 times arranged next to each other. - It should be like a cartoon where an image moves by 100% (margin: -100%) and generates a feeling of a movie.
However, this results in an image width of 1920px x 41pics = 78720px.
This is of an enormous width, but what I am wondering about is that the filesize is only 975kB which is in my opinion not that big!? - However, somehow it takes a very long time to load the picture in the Webbrowser and the image is not of such quality as in my ImageViewer on Desktop.
Question 1: What do I have to consider when dealing with such a big image-width? What are the limits?
Question 2: Is there a better way make such kind of a slideshow? - Consider that the sliding itself shouldn't be visible. It should be like a movie based on about 40 pictures.
Thanks in advance!
PNG compresses very well, especially if it's a cartoon like you say that may use only a limited number of colours.
However, when loaded into memory, the device must load all that pixel data into RAM to display it. That's almost 80 million pixels in your case, which would be around 320Mb of uncompressed data. This is probably why the browser is struggling, and especially so if you're using margin to move it around as that requires a full re-draw of the image.
You may have better results with transform, as this should use hardware acceleration and also avoids the reflow part of a redraw since transforms don't affect page layout.
But the better solution would be to break it down into individual images. Have your code load in the next image, scroll it across, then load the next while scrolling and unload the one that's now off-screen to provide a relatively seamless view.
I have an image with the dimensions of 5534 × 3803, and size of 2.4mb. The UIView references notes that:
"In iOS 3.0 and later, views are no longer restricted to this maximum
size but are still limited by the amount of memory they consume."
When the image loads, it lags for half a second, then slides in. The image sits in the UIImageView at 1024x704, but can be scaled up to 4x that size for the purpose of my app.
Are you able to preload the image in the AppDelegate? Or is there another way of working around having such a large image?
Thanks
EDIT: The scaling is done via UIPinchGestureRecognizer, and scales up and done (scale x4 - x1) based on the image's center point. There is no panning of the image when zoomed in.
Personally, I would try to write a tile-based system (think Google Maps) that slices your big image into a grid of small images to avoid loading in that gigantic image all at once into RAM. I don't really know what your user interactions are for this image, or whether the images are changing or baked into your project, but I'd assume you can let users scroll around since that image is bigger than any iOS screen. With a tile-based system, you only load the images that are on-screen. CATiledLayer is an Apple class for doing just such a thing. That's probably what you want to look into.
See this StackOverflow question for some different approaches. The accepted answer uses code from Apple's sample PhotoScroller project, which may work for your needs and uses CATiledLayer.
This ScrollViewSuite Apple code might also get on your way (check out the Tiling code).
Ok, here's my problem. I have a HUGE jpg file, 18000 x 18000 pixels 41MB in size.
If you really need to know, it's a map of a section of the country with services.
My project is really simple. I just need to be able to zoom and display this granddaddy size image. All the way from aspect fit to 100% on the iPhone. I'm not too sure if this can be done or how long it will take. Would appreciate any insights.
I have tried using imageView but I read that it really shouldnt exceed 1024 x 1024. That is way below what I have. If you have an idea how to go about doing this, please share!
You should split the image into tiles, at a range of magnifications. Calculate and build these off-line, and ship them as individual files in the app bundle. Given the zoom in your display, pick the closest zoom size. You then select which tiles are needed to cover the screen, and make a grid of them. As the user zooms, select the appropriate tile size.
The benefit of this is that you don't ever have to load HUGE files into memory, only as much as needed.
This is how Google maps does it.
Can't give you any code, sorry!
You should follow an approach similar to what Google Maps and other map sites do. You need to slice the whole map in sections, so the users don't need to load the whole map if it's not always necessary (plus makes loading time way faster)
There's a couple of solutions that might work for you like OpenLayers or even creating a Custom Google Map with your images as seen here and here
Here is an example from Apple for processing large images called PhotoScroller. The images have already been tiled. If you need an example of tiling an image in Cocoa check out cimgf.com
i am converting the image into thumbnail format and sending it to server and i want to convert it back to original size while receiving can any one please tell me how to resize the image to original without loosing quality.....
i tried directly to displaying the image in image view but the quality of the image is missing ...
can any one please help me how to maintain the quality of the image .......
Downscaling is irreversible, some information lost forever.
What you're asking isn't possible. You can't enlarge an image while maintaining the same quality. If you think about an image as a mapped array of pixels (literally, a "bit-map"), this makes sense. The image is saved with a fixed amount of data, and that's all you have to work with when you resize it. Any examples to the contrary (like TV shows) are purely fictional.
Investigate using vector graphics instead, which can be resized at will without a loss of quality.
you simply can not convert an image from thumbnail to original size and retain the quality it had in its original size.
if you want to display the image full-size, you have to send the full-size image.
You could think about using a Vector image? They do not lose quality when resized. But I have no clue whether you can use them for thumbnails in iOS.
See this wiki page for more info about Vector graphics.
I'm writing a card game for the iPhone, and I'm not sure about the best strategy for displaying the cards. I have a basic prototype that creates a UIImageView that can be dragged for each card with a dummy image. I wanted to use one large UIImage that contains the faces of all of the cards, and then have each draggable UIImageView display a part of that image. I must be misunderstanding what setBounds is for - I thought that controlled which part of the underlying image is displayed. So, two questions:
Is this the right approach?
How do I display just a part of the image?
Depending on your resolution, this might not be the best approach.
From Apple:
You should avoid creating UIImage
objects that are greater than 1024 x
1024 in size. Besides the large amount
of memory such an image would consume,
you may run into problems when using
the image as a texture in OpenGL ES or
when drawing the image to a view or
layer. This size restriction does not
apply if you are performing code-based
manipulations, such as resizing an
image larger than 1024 x 1024 pixels
by drawing it to a bitmap-backed
graphics context. In fact, you may
need to resize an image in this manner
(or break it into several smaller
images) in order to draw it to one of
your views.
Now, you are talking about breaking it up into several smaller pieces, but given UIIMage's caching, I am not sure what happens to memory every time you access the image and copy a sub-rect out of it. I think the approach I would take is to have an array of images, instead of one big one.