Resize PDF NSImage OSX

Question

I'm updating an image resizing Mac App. What I want to be able to do is if the user imports an image to be resized that has a PDFImageRep, save a new PDF file with a resolution of my choosing.

So far I've tried to draw the image at a new size, as in:

- (NSImage*)imageAtSize:(NSSize)newSize
{
    NSImage *resizedImage = [[NSImage alloc] initWithSize:newSize];

    [resizedImage lockFocus];
    [self drawInRect:NSMakeRect(0, 0, newSize.width, newSize.height)
            fromRect:NSMakeRect(0, 0, self.size.width, self.size.height)
           operation:NSCompositeSourceOver fraction:1.0];
    [resizedImage unlockFocus];

    return resizedImage;
}

but this loses the PDF image rep, and therefore makes my saving code fail.

- (void)saveAsPDFWithOutputDirectory:(NSURL *)outputDirectory size:(NSSize)newSize
{
    NSPDFImageRep *pdfRep = [self PDFImageRep];
    [pdfRep setSize:newSize];

    NSError *error = nil;
    [pdfRep.PDFRepresentation writeToURL:outputDirectory options:NSDataWritingAtomic error:&error];
    if (error)
    {
        CLS_LOG(@"Error saving image: %@", error);
    }
}

So how do I do it. The images I'm going to be using should be vector based, so is there some way I could just update a property on the PDF to specify a new resolution?

Answer 1

Try the following approach. This creates a new PDF data object that you can save into a file.

// pdfData is a CFMutableDataRef
// auxInfo is a CFDictionary
// bounds is your new size in points!
CGDataConsumerRef consumer = CGDataConsumerCreateWithCFData(pdfData);
CGContextRef context = CGPDFContextCreate(consumer, &bounds, auxInfo);
CGPDFContextBeginPage(context, NULL);
NSGraphicsContext *gc = [NSGraphicsContext graphicsContextWithGraphicsPort:context flipped:NO];
[NSGraphicsContext saveGraphicsState];
[NSGraphicsContext setCurrentContext:gc];

// Your drawing code here
// You probably want to draw your NSImage here in the bounds

[NSGraphicsContext restoreGraphicsState];
CGPDFContextEndPage(context);
CGPDFContextClose(context);
CGContextRelease(context);
CGDataConsumerRelease(consumer);

Then save pdfData to file