iPhone: How to change camera photo quality

I've not found a answer to this question anywhere, but this seems like a typical problem: I am taking pictures from an iPhone 4, and I have to send these pics to a server through a POST-Request, but the开发者_如何学编程 server does not accept pictures that are bigger than 0,5 MB, so I have to compress the pictures before I send them. In order to achieve this, I am calling following method: "NSData *imageData = UIImageJPEGRepresentation(tempImage, 0.7);", which means: I am compriming the image data, and it takes a lot of time (about 10s / pic).

Is there any way to control the quality of the camera device in order to take low quality pictures?

Thanks in advance for helping.

Anything that will block the main thread should be done in a background thread, including converting an image to a JPEG. So you should start the JPEG conversion using performSelectorInBackground:withObject: and, when the conversion is done, pass the resulting NSData object back to the main thread.

- (void)imagePickerController:(UIImagePickerController *)picker
didFinishPickingMediaWithInfo:(NSDictionary *)info {
    UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];
    [self dismissModalViewControllerAnimated:YES];
    [self performSelectorInBackground:@selector(encodePhotoInBackground:) withObject:image];
}

- (void)encodePhotoInBackground:(UIImage*)image {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    NSData *imageData = UIImageJPEGRepresentation(image, 0.60);

    [self performSelectorOnMainThread:@selector(saveImageData:) withObject:imageData waitUntilDone:NO];

    [pool release];
}

- (void)saveImageData:(NSData*)imageData {
    // Do something with the image
}