Exporting unshown NSViewController to JPG - objective-c

Question

I am working on an desktop app that generates an image from en NSViewController that is not shown.
The view generated has 3 NSImageViews which change the content once created.
I manage to export the NSViewController's view to JPG file, but it never renders in the image given to the NSImageView, it keeps the image which is set in the nib. Also, if I don't set the background color to the view's layer... I get an empty result.
What am I missing here? I guess I need to update the NSViewController's view... but how can I do that? I do not want to show my NSViewController.
My code:
- (IBAction)doExport:(id)sender {
ExportView *view = [[ExportView alloc] initWithNibName:#"ExportView" bundle:nil];
[view.pic1 setImage:self.pic1.image];
[view.pic2 setImage:self.pic2.image];
[view.pic3 setImage:self.pic3.image];
[view.icon setImage:self.icon.image];
// Hardcoding for test
[view.pic1 setImage:[NSImage imageNamed:#"iPhone 4-Inch Screenshot 1"]];
[view.pic1 setNeedsLayout:YES];
[view.pic1 setNeedsDisplay];
[view.pic1 updateLayer];
// Setup the image to render
NSRect imgRect = view.view.frame;
NSSize imgSize = imgRect.size;
NSBitmapImageRep *rep = [[NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL
pixelsWide:imgSize.width
pixelsHigh:imgSize.height
bitsPerSample:8
samplesPerPixel:4
hasAlpha:YES
isPlanar:NO
colorSpaceName:NSDeviceRGBColorSpace
bitmapFormat:NSAlphaFirstBitmapFormat
bytesPerRow:0
bitsPerPixel:0];
NSGraphicsContext *g = [NSGraphicsContext graphicsContextWithBitmapImageRep:rep];
[NSGraphicsContext saveGraphicsState];
[NSGraphicsContext setCurrentContext:g];
// Set view background color
CALayer *viewLayer = [CALayer layer];
[viewLayer setBackgroundColor:[NSColor clearColor].CGColor];
[view.view setWantsLayer:YES];
[view.view setLayer:viewLayer];
// Render
CGContextRef zCgContextRef = (CGContextRef) [g graphicsPort];
[[view.view layer] renderInContext:zCgContextRef];
// Render pic as well, for test
[view.pic1.layer renderInContext:zCgContextRef];
// Get the Data for the image
NSData *exportedData = [rep representationUsingType:NSJPEGFileType properties:nil];
// Start the savepanel
NSSavePanel *savepanel = [NSSavePanel savePanel];
savepanel.title = #"Save chart";
[savepanel setAllowedFileTypes:[NSArray arrayWithObject:#"jpg"]];
[savepanel beginSheetModalForWindow:self.window completionHandler:^(NSInteger result)
{
if (NSFileHandlingPanelOKButton == result)
{
NSURL* fileURL = [savepanel URL];
if ([fileURL.pathExtension isEqualToString:#""])
fileURL = [fileURL URLByAppendingPathExtension:#"jpg"];
[exportedData writeToURL:fileURL atomically:YES];
}
}];
}

Answer 1

I solved it in a very ugly way. Basically what I do is I add the view to my contentView and set setHidden to YES straight away. This will intialize the view. Now I change the content of my Nib view.
When its time to render the data to NSData I change setHidden to NO, generate the NSData and then remove the view.
The end result (no beautiful code :( ):
- (IBAction)doExport:(id)sender {
ExportView *view = [[ExportView alloc] initWithNibName:#"ExportView" bundle:nil];
[view.view setHidden:YES];
[self.window.contentView addSubview:view.view];
[view.pic1 setImage:self.pic1.image];
[view.pic2 setImage:self.pic2.image];
[view.pic3 setImage:self.pic3.image];
[view.icon setImage:self.icon.image];
// Setup the image to render
NSRect imgRect = view.view.frame;
NSSize imgSize = imgRect.size;
NSBitmapImageRep *rep = [[NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL
pixelsWide:imgSize.width
pixelsHigh:imgSize.height
bitsPerSample:8
samplesPerPixel:4
hasAlpha:YES
isPlanar:NO
colorSpaceName:NSDeviceRGBColorSpace
bitmapFormat:NSAlphaFirstBitmapFormat
bytesPerRow:0
bitsPerPixel:0];
NSGraphicsContext *g = [NSGraphicsContext graphicsContextWithBitmapImageRep:rep];
[NSGraphicsContext saveGraphicsState];
[NSGraphicsContext setCurrentContext:g];
// Set view background color
CALayer *viewLayer = [CALayer layer];
[viewLayer setBackgroundColor:[NSColor clearColor].CGColor];
[view.view setWantsLayer:YES];
[view.view setLayer:viewLayer];
[view.view setHidden:NO];
// Render
CGContextRef zCgContextRef = (CGContextRef) [g graphicsPort];
[[view.view layer] renderInContext:zCgContextRef];
[view.view removeFromSuperview];
// Get the Data for the image
NSData *exportedData = [rep representationUsingType:NSJPEGFileType properties:nil];
// Start the savepanel
NSSavePanel *savepanel = [NSSavePanel savePanel];
savepanel.title = #"Save chart";
[savepanel setAllowedFileTypes:[NSArray arrayWithObject:#"jpg"]];
[savepanel setNameFieldStringValue:#"Test"];
[savepanel beginSheetModalForWindow:self.window completionHandler:^(NSInteger result)
{
if (NSFileHandlingPanelOKButton == result)
{
NSURL* fileURL = [savepanel URL];
if ([fileURL.pathExtension isEqualToString:#""])
fileURL = [fileURL URLByAppendingPathExtension:#"jpg"];
[exportedData writeToURL:fileURL atomically:YES];
}
}];
}