How to get the QLPreviewView Content and write to an image - objective-c

Question

I just write a small demo. All of its feature is use the QLPreviewView to give a quick look of a Pages file.
When the App runs, you can scroll to view the Pages file content, and when you click save to PNG button, the app will save the current content displayed into a PNG image file. You can get the implementation in the save method. I just tried two implementation in that method, neither of them worked.
I just got a blank image filled with the window background color. Some advise here? Thanks.
The code and the App screen shot can be found here http://dr.ibuick.com/updU
#import <Cocoa/Cocoa.h>
#import <Quartz/Quartz.h>
#import <QuickLook/QuickLook.h>
#import "IBAppDelegate.h"
#interface IBAppDelegate (QLPreviewItem) <QLPreviewItem>
#end
#implementation IBAppDelegate (QLPreviewItem)
- (NSURL *)previewItemURL
{
return self.resolvedFileURL;
}
- (NSString *)previewItemTitle
{
return [self.originalURL absoluteString];
}
#end
#implementation IBAppDelegate
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
_resolvedFileURL = [NSURL fileURLWithPath:#"/Users/buick/Desktop/1.pages"];
_originalURL = [NSURL fileURLWithPath:#"/Users/buick/Desktop/1.pages"];
_previewView = [[QLPreviewView alloc] initWithFrame:NSMakeRect(0, 50, 480, 360)
style:QLPreviewViewStyleNormal];
[_previewView setPreviewItem:self];
[self.window.contentView addSubview:_previewView];
}
- (IBAction)save:(id)sender {
// Method 1
[_previewView lockFocus];
NSBitmapImageRep* rep = [_previewView
bitmapImageRepForCachingDisplayInRect:_previewView.bounds];
[_previewView cacheDisplayInRect:_previewView.bounds toBitmapImageRep:rep];
[_previewView unlockFocus];
[[rep representationUsingType:NSPNGFileType properties:nil]
writeToFile:#"/Users/buick/Desktop/1.png" atomically:YES];
// Method 2
[_previewView lockFocus];
NSBitmapImageRep *bits;
bits = [[NSBitmapImageRep alloc]
initWithFocusedViewRect:[_previewView visibleRect]];
[_previewView unlockFocus];
NSData *imageData;
NSDictionary *imageProps = [NSDictionary dictionaryWithObject:[NSNumber
numberWithFloat:0.9] forKey:NSImageCompressionFactor];
imageData = [bits representationUsingType:NSJPEGFileType
properties:imageProps];
[imageData writeToFile:#"/Users/buick/Desktop/1.png" atomically:YES];
}
#end

Answer 1

OK I think I got it. Try setting your QLPreviewView type to QLPreviewViewStyleCompact when you init it.
pv = [[QLPreviewView alloc] initWithFrame:pv.bounds
style:QLPreviewViewStyleCompact];
Then use this category
NSImage+QuickLook from Matt Gemmel...
github
NSImage *image = [NSImage imageWithPreviewOfFileAtPath:[[self.files objectAtIndex:i] path] ofSize:NSMakeSize(1200, 1920) asIcon:NO];