Is it possibile get thumbail image from .doc or .xls document?

Question

I'm looking for create an image thumbnail from a MS doc/xls document's page, but I found nothing about it.

For pdf documents I used Quarz framework, but I can't in this case.

Some help?

Answer 1

A web view can be used for making a MS doc preview.

I've tried once to do that with this piece of code. It works ... but ... the web view need to work in graphical thread, so when this operation is running your interface is slower. Maybe can you optimized that.

Header

@interface WebViewThumbnailGenerationOperation: NSOperation <UIWebViewDelegate> {
    BOOL finished;
}
@property(nonatomic,retain) NSURL* documentURL;
@property(nonatomic,retain) UIWebView* webView;

-(void)saveThumbnail:(UIImage*)thumbnail;

@end

Code

/**************************************************************************************************/
#pragma mark - WebViewBased Thumbnails

@implementation WebViewThumbnailGenerationOperation

@synthesize documentURL,webView;

-(void)dealloc {
    RELEASE_SAFELY(documentURL);
    [super dealloc];
}


- (void)loadWebView {
    if (self.isCancelled) {
        return;
    }
    self.webView = [[[UIWebView alloc] init] autorelease];
    self.webView.delegate = self;
    self.webView.scalesPageToFit = YES;
    self.webView.frame = CGRectMake(0, 0, 290, 290);
    NSURLRequest *request = [NSURLRequest requestWithURL:documentURL];
    [self.webView loadRequest:request];    
}

- (void)webViewDidFinishLoad:(UIWebView *)webView {
    if (self.isCancelled) {
        return;
    }
    UIGraphicsBeginImageContext(CGSizeMake(290,290));
    CGContextRef context = UIGraphicsGetCurrentContext();
    [self.webView.layer renderInContext:context];
    UIImage *thumbnail = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    [self performSelectorInBackground:@selector(saveThumbnail:) withObject:thumbnail];

    self.webView = nil;
}

-(void)saveThumbnail:(UIImage*)thumbnail {
    NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
    if (self.isCancelled) {
        return;
    }

    if(!thumbnail) {
        return;
    }

    NSData* thumbnailData = UIImageJPEGRepresentation(thumbnail,0.8);
    [IOHelper saveThumbnailData:thumbnailData forDocumentURL:documentURL];

    [self willChangeValueForKey:@"isFinished"];
    finished = YES;
    [self didChangeValueForKey:@"isFinished"];

    [pool release];
}

-(void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error {
    NSLog(@"Preview failed for %@ error %@",document.name,error);
    [self willChangeValueForKey:@"isFinished"];
    finished = YES;
    [self didChangeValueForKey:@"isFinished"];
    self.webView = nil;
}

-(void)start {
    finished = NO;
    [super start];
}

- (void)main {
    if (self.isCancelled) {
        return;
    }
    [self performSelectorOnMainThread:@selector(loadWebView) withObject:nil waitUntilDone:YES];
}

-(BOOL)isFinished {
    return finished;
}

@end

Edit: ARC version!

Header

@interface WebViewThumbnailGenerationOperation: NSOperation <UIWebViewDelegate>

@property(nonatomic, strong) NSURL* documentURL;
@property(nonatomic, strong) UIWebView* webView;
@property(nonatomic) BOOL finished;


-(void)saveThumbnail:(UIImage*)thumbnail;

@end

Code

/**************************************************************************************************/
#pragma mark - WebViewBased Thumbnails

@implementation WebViewThumbnailGenerationOperation

- (void)loadWebView {
    if (self.isCancelled) {
        return;
    }
    self.webView = [[UIWebView alloc] init];
    self.webView.delegate = self;
    self.webView.scalesPageToFit = YES;
    self.webView.frame = CGRectMake(0, 0, 290, 290);
    NSURLRequest *request = [NSURLRequest requestWithURL:documentURL];
    [self.webView loadRequest:request];    
}

- (void)webViewDidFinishLoad:(UIWebView *)webView {
    if (self.isCancelled) {
        return;
    }
    UIGraphicsBeginImageContext(CGSizeMake(290,290));
    CGContextRef context = UIGraphicsGetCurrentContext();
    [self.webView.layer renderInContext:context];
    UIImage *thumbnail = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    [self performSelectorInBackground:@selector(saveThumbnail:) withObject:thumbnail];

    self.webView = nil;
}

-(void)saveThumbnail:(UIImage*)thumbnail {
    @autoreleasepool {
        if (self.isCancelled) {
            return;
        }

        if(!thumbnail) {
            return;
        }

        NSData* thumbnailData = UIImageJPEGRepresentation(thumbnail,0.8);
        [IOHelper saveThumbnailData:thumbnailData forDocumentURL:documentURL];

        [self willChangeValueForKey:@"isFinished"];
        finished = YES;
        [self didChangeValueForKey:@"isFinished"];

    }
}

-(void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error {
    NSLog(@"Preview failed for %@ error %@", document.name, error);
    [self willChangeValueForKey:@"isFinished"];
    finished = YES;
    [self didChangeValueForKey:@"isFinished"];
    self.webView = nil;
}

-(void)start {
    finished = NO;
    [super start];
}

- (void)main {
    if (self.isCancelled) {
        return;
    }
    [self performSelectorOnMainThread:@selector(loadWebView) withObject:nil waitUntilDone:YES];
}

-(BOOL)isFinished {
    return finished;
}

@end