glReadPixels and save to image

Posted by Julius Petraška on Stack Overflow See other posts from Stack Overflow or by Julius Petraška
Published on 2012-10-09T15:30:18Z Indexed on 2012/10/09 15:37 UTC
Read the original article Hit count: 258

Filed under:

objective-c

|

osx

|

opengl

I have app, where user drags and drops image, and it is being redrawn with OpenGL for some aviable processing. Everything works. And when user wants to save his image it works like that:

glReadPixels -> NSBitmapImageRep -> NSData -> Write to file

This works too. Almost. With some images it is not working as it should work.

For example:

.png

when I open and save this image: enter image description here

I get:
enter image description here

And if I open and save this image: enter image description here

I get:
enter image description here

.jpg

If I open and save:
enter image description here

I get:
enter image description here

And when I open and save:
enter image description here

I get:
enter image description here

So sometimes images saves badly. Why is it happening?

© Stack Overflow or respective owner

Related posts about objective-c

Blocking access to websites with objective-C / root privileges in objective-C

as seen on Stack Overflow - Search for 'Stack Overflow'
I am writing a program in Objective-C (XCode 3.2, on Snow Leopard) that is capable of either selectively blocking certain sites for a duration or only allow certain sites (and thus block all others) for a duration. The reasoning behind this program is rather simple. I tend to get distracted when I… >>> More
Objective-C with some Objective-C++, calling a normal c++ method "referenced from" problem

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I made an Objective-C project for the iPhone. I had only one cpp class, the soundEngine taken from some Apple demo. Now I'm trying to merge OpenFeint which is coded in Objective-C++. As soon as I drop in the code without even referring to it from my code, when I hit Build, my Objective-C code… >>> More
Add an objective @property attribute in objective-c

as seen on Stack Overflow - Search for 'Stack Overflow'
Does anyone know of a way to add additional attribute types to the @property keyword without modifying the compiler? Or can anyone think of another way to genericize getter/setter creation? Basically, I have a lot of cases in a recent project where it's handy for objects to lazily instantiate their… >>> More
ObjectiveC builtin template system ?

as seen on Stack Overflow - Search for 'Stack Overflow'
I am developing an iPhone application and I use HTML to display formatted text. I often display the same webpage, but with a different content. I would like to use a template HTML file, and then fill it with my diffent values. I wonder if ObjectiveC has a template system similar to ERB in Ruby. That… >>> More
ObjectiveC Syntax for Specifying Protocol Name in Method Argument

as seen on Stack Overflow - Search for 'Stack Overflow'
What's the ObjectiveC syntax for specifying a protocol as an argument in a method? Say I have 2 protocols, MyProtocol and MyProtocolCB: @protocol MyProtocolCB <NSObject> - (void) func; @end @protocol MyProtocol <NSObject> - (void) register:(MyProtocolCB*) cb; @end I'm receiving this… >>> More

Related posts about osx

OSX/Wine - Associating file extension (.php) with a Windows program on OSX

as seen on Super User - Search for 'Super User'
Greetings, I am running PSPad (a Windows programming editor) on OSX/Snow Leopard using Wine 1.1.35 I want to associate various file extensions (.php, .js, .html) with PSPad.exe OSX Finder does not allow this association -- I can only associate file types with $.app items in Applications. How do… >>> More
osx web service spawns icon in taskbar - osx - while drawing image

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a web endpoint that displays an image of a string... When the following code is run (in tomcat) it spawns a java icon in the taskbar on OSX. Not sure if it is a problem, or whats going on. Looking for some sort of explination @RequestMapping("/text/{text}") public void textImage(HttpServletResponse… >>> More
Cannot disable spotlight indexing on volume

as seen on Super User - Search for 'Super User'
I have a FAT32 partition on my HDD. When using OSX, it is mounted to /Volumes/MEDIA. After a recent upgrade to Mavericks, spotlight is having trouble indexing it, eating up almost all of my system resources, and I cannot get the indexing to stop: [jay-mba-osx ~]% sudo mdutil -v -a -i off /: Indexing… >>> More
OSX - User home directories shared via NFS

as seen on Super User - Search for 'Super User'
Hi, I've run into some problems with how I've got user home directories set up on our system here. Our server is an XServe, using Open Directory to manage the user accounts. The majority of our workstations are OSX, but there are a few running Linux (Centos 5.3), and, as time goes on, we expect… >>> More
Can't connect to local IP address on OSX

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm trying to connect to a webserver that's running on my mac OSX 1.6. I'm able to connect to it locally using http://127.0.0.1:8888/myapp but when I attempt to connect to it using my machine's local IP address (http://192.168.1.15:8888/myapp IP shown below) from the same machine (or another on the… >>> More