I have a PDF reader that displays pages of the document. What I want to do is allow the user to draw over the PDF in a transparent view. Then I want to save the drawing (UIImage) to disk. If at all possible, I don't want to have the documents folder filled with files like documentName_page01.png, documentName_page02.png for every page that is drawn over.
However, I can't figure out how to store these UIImages into a single file without it becoming unwieldy and memory intensive.
Any ideas appreciated.
What is the user drawing, just lines, rectangles, circles and so on? Maybe store colors and paths of what needs to be drawn, put all of that into an NSArray and serialise that. That might be easier than trying to put multiple UIImages into a file, will use up less space on the device, and might be faster to load. Then just recreate the drawings.
Use Core Data to store your images in Binary Data fields and retrieve them from there. This way, you won't fill your Documents folder with images, no matter how many PDFs of how many pages you have. Here's a tutorial showing you how to do this.
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I am newly in iOS development.I have to make an application for a car dealer in which i have to show different cars with different colors.Please tell me the best way because i have to fetch lots of images every time from the web server.How can i reduce the rendering time in fetching the images.
Please consider i am very new in ios development and need your help.
If you have any sample application please share it with me.
You can use DB to store images as BLOB and also fetch images only when there is update at server.
First, make sure you send images that are no larger than needed.
If you have a list view that shows pictures of the cars, have a webservice send you premade thumbnails that are (preferably) exactly the right size.
Second, Make sure the images are loaded separately from the data set.
The best place to do this, would be in the controllers for your UITableViewCell.
Just have your UITableViewCell start their own thread to download and display the image as soon as they come into view.
Third; caching.
Make sure you save local copies of the thumbnails, and make sure the Table View Cells search for local copies of the images, and load those instead of downloading them if they are already locally present.
you can do:-
use lazy loading
use paging
use predicates for searches
use fast enumeration
these things in general will keep your app smooth
If you are going to show images in UITableView then you can use lazy loading. It will load images only for the displayed rows and once image for any row index has been downloaded, it will not repeat downloading for that row index. So its faster and useful.
I have a bunch (about 20)thumbnail jpg images that I want to enlarge to a much bigger image when you click on each thumbnail. But I dont want to have so many large jpgs on my website, because that will slow down the entire site.
Whats the best way to enable the user to view the thumbnail in large without making them into big jpg images?
I need the enlarged image to be as big as possible, because each one has text that I want the user to be able to read easily.
The link to my site is www.totalrecallsolutions.com
I dont want to make them into pdf's because not everyone has a pdf viewer, and I dont want to make them download it.
I also dont want to code each image onto its own webpage, even though I know that that will be able to be as big as I want, because I dont want to spend all that much time.
Any other options?
Thanks!
I have a bunch (about 20)thumbnail jpg images that I want to enlarge
to a much bigger image when you click on each thumbnail. But I dont
want to have so many large jpgs on my website, because that will slow
down the entire site.
I'm a little confused. You don't want to host the images, or you don't want them embedded? If you don't want to host them, use something like photobucket. If you don't want them directly embbeded to your page, look at javascript popup windows.
I'm taking images from the camera or the camera roll and I'm saving them to core data using an ImageToDataTransformer class. I need to use these saved images in two different places in my app: 250x250 imageview and 50x50 imageview.
First, should I use png format for both imageviews?
Second, can I compress the image before I save it to core data, and what's the best way?
Third, should I save two different images, one for the big image and another for the thumbnail in a different view?
When Xcode builds your project, it automatically optimizes PNG files included in your project. So, I guess you should use PNG.
I don't know about runtime.
That would be a good idea if you have a table view and you want to show thumbnails. You wouldn't want to be loading the huge files, that would be excruciatingly slow.
I'm rendering a PDF file on my iPad using a graphics PDF context. The PDFs vary in size but may be up to 90 pages. I need a background image on each page but if I simply draw it the PDF file size will be way larger. Is there a way to kinda only add it once and 'share' it somehow across pages?
Thanks
The PDF format specification enables you to re-use objects "by reference". You can re-use any object multiple times that is defined only once. Usually that happens with fonts, logos, background images, watermarks, ICC profiles, ....
I did a test where I repeated a background image behind each PDF page. Surprisingly, the file size increased by a single and constant amount, regardless of the number of pages with repeated backgrounds.
The verdict: The drawing to PDF context libraries are smarter than you might think.
What is the best way to use the custom UI graphics on the iPhone?
I have come across CGContextDrawPDFPage and Panic's Shrinkit. Should I be using PDF's to store my vector ui graphics and loading them using CGContextDrawPDFPage to draw them.
Previously I asked what way Apple store their UI graphics and was answered crushed png. The options are I can think of are below, but I'm also interested in any other techniques...
PNG (bitmapped image)
Custom UIView drawing code (generated from Opacity)
PDF (I've not used this method, is it with CGContextDrawPDFPage?)
This question is for vector graphics only (but I guess some people may only use bitmapped?). Looking for what is standard / most effective / most efficient.
Edit: Bounty added, I'm interested to hear the process of anyone who works with UI designers, or are themselves a UI designer. And pointers on resolution independence i.e. for iPad / iPhone HD future proofing.
Many thanks
Ross
I can suggest 3 different ways, 2 of which you already mentioned:
Creating custom UIView.
Drawing in a CGLayer.
loading from PDF.
Each have their advantages, depending on what you want to do:
UIView vs CGLayer
In terms of performance (for one-time drawing) and ease of use there shouldn't be much difference between the two (there are minor differences, but nothing serious). Apparently Opacity can export source code for both (I haven't personally used it). That said, there are things you should consider before choosing:
If you have a fixed image (which your question suggests so), use CGLayer. CGLayer objects will be cached on the graphics device, so re-using them is much faster. Even if the cache is cleared, you're still using the same object for redrawing, meaning there's no need for re-creating it.
On the other hand, if you need to change your drawing as the user interacts with the app, UIView could be faster, as you have the flexibility of updating just one part of the image instead of the whole view.
CGLayer is independent of the UI. So the same code works fine for Mac/iPhone/iPad, or even for saving to files.
Conclusion: Use CGLayer, unless it's a special case.
CGLayer (In code drawing) vs PDF (loading from file)
I don't have any benchmark for this, but I expect CGLayer to be slightly faster: (1) there's no need to read a file. (2) the pdf commands should be converted to system's graphic elements, which is more or less the same as creating a CGLayer. (3) I'm not sure about how pdf pages are cached, but I don't expect it to be faster than CGLayer. Anyway, all this shouldn't make much difference unless you want optimization till the last millisec. Again, the choice should be based on your use case:
CGLayer gives you more flexibility in the code. Your only access to a pdf page is through CGContextDrawPDFPage, which means even simple tasks such as scaling/transforming the drawing will be harder.
Using PDFs on the other hand, is more flexible after finishing the code. You can simply update the pdf file with a new whenever you want, load it from the web, etc. .
Creating a pdf could be easier than coding the drawing. You can use any app you want, you don't need to worry about the API and system resources. After all, the code can output a pdf file, not the other way around.
Conclusion: If you don't need to do much with the drawing (just want to show an icon or something), go with the pdf. if you need to work on it in the app, consider CGLayer.
Of course you could always mix the approaches as you see fit: e.g. Load a pdf file, put it in a CGLayer to adjust it, draw it with a UIView where you can put a badge on it!
I stumbled over this question because I have a question about PDFs too. I'm working together with a UI designer and we are succesfully using PDFs to create UI elements. For example: For a button we have 3 PDFs for ON, OFF and the shadow. I wrote a piece of code that transformes a PDF into a UIImage. It can scale the resulting image and even colorize it to have one template for many styles of buttons. It works pretty good :)
Our problem is that we can't scale up the vector graphics without quality loss. That's why we decided to use graphics that are big enough and we only have to scale them down. But I still wonder if there's a way to scale up a PDF before drawing it to a context and create a UIImage. Here's my post.