pdf2png.m

// A tiny program that converts PDF documents to high resolution PNG images.
//
// gcc --std=c99 -Wall -g -o pdf2png pdf2png.m -framework Cocoa
//
// Written by Evan Jones <[email protected]> Februrary, 2004
// http://www.eng.uwaterloo.ca/~ejones/
//
// Released under the "do whatever you want" public domain licence.

#include <Cocoa/Cocoa.h>

int main( int argc, char* argv[] )
{
        int desiredResolution = 200; // in DPI

        BOOL morePages = YES;
        int page = 1;

        NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

        // Package all arguments as NSStrings in an NSArray
        NSMutableArray* args = [NSMutableArray arrayWithCapacity: argc - 1];
        for ( int i = 1; i < argc; ++ i )
        {
                [args addObject: [NSString stringWithCString: argv[i]] ];
        }

        // If we have a "--dpi" along with a corresponding argument ...
        unsigned int index = NSNotFound;
        if ( (index = [args indexOfObject: @"--dpi"]) != NSNotFound && index + 1 < [args count] )
        {
                // Parse it as an integer
                desiredResolution = [[args objectAtIndex: index + 1] intValue];
                [args removeObjectAtIndex: index + 1];
                [args removeObjectAtIndex: index];
        }

        // If we have a "--page" along with a corresponding argument ...
        if ( (index = [args indexOfObject: @"--page"]) != NSNotFound && index + 1 < [args count] )
        {
                // Parse it as an integer
                page = [[args objectAtIndex: index + 1] intValue];
                morePages = NO;
                [args removeObjectAtIndex: index + 1];
                [args removeObjectAtIndex: index];
        }

        if ( [args count] != 1 || [args indexOfObject: @"--help"] != NSNotFound || desiredResolution <= 0 || page <= 0 )
        {
                fprintf( stderr, "pdf2png [options] file\n" );
                fprintf( stderr, "\t--dpi dpi\tSpecifies the resolution at which to export the pages\n" );
                fprintf( stderr, "\t--page page\tSingle page to export\n" );
                fprintf( stderr, "\t--help\tPrint this help message\n" );
                return 1;
        }




        NSString* sourcePath = [args objectAtIndex: 0];
        NSImage* source = [ [NSImage alloc] initWithContentsOfFile: sourcePath ];
        [source setScalesWhenResized: YES];

        // Tip from http://www.omnigroup.com/mailman/archive/macosx-dev/2002-February/023366.html
        // Allows setCurrentPage to do anything
        [source setDataRetained: YES];

        if ( source == nil )
        {
                fprintf( stderr, "Source image '%s' could not be loaded\n", argv[1] );
                return 2;
        }

        // The output file name
        NSString* outputFileFormat = @"%@-p%01d";

        // Find the PDF representation
        NSPDFImageRep* pdfSource = NULL;
        NSArray* reps = [source representations];
        for ( int i = 0; i < [reps count] && pdfSource == NULL; ++ i )
        {
                if ( [[reps objectAtIndex: i] isKindOfClass: [NSPDFImageRep class]] )
                {
                        pdfSource = [reps objectAtIndex: i];
                        [pdfSource setCurrentPage: page-1];

                        // Set the output format to have the correct number of leading zeros
                        unsigned int numDigits = [(NSString*) [NSString stringWithFormat: @"%d", [pdfSource pageCount]] length];
                        outputFileFormat = [NSString stringWithFormat: @"%%@-p%%0%dd", numDigits];
                }
        }

        NSSize sourceSize = [source size];

        // When loading a PDF document, it reports size in typographic dots. There are 72 dots per inch.
        // See http://www.macosxguru.net/article.php?story=20031209091834195
        // When converting, we need to scale the PDF by this factor
        double sourceResolution = 72.0;
        int pixels = [ [source bestRepresentationForDevice: nil] pixelsWide];
        if ( pixels != 0 ) sourceResolution = ((double)pixels / sourceSize.width) * 72.0;
        double scaleFactor = desiredResolution / sourceResolution;

        NSSize size = NSMakeSize( sourceSize.width * scaleFactor, sourceSize.height * scaleFactor );


        [NSApplication sharedApplication];
        [[NSGraphicsContext currentContext] setImageInterpolation: NSImageInterpolationHigh];

        [source setSize: size];
        NSRect destinationRect = NSMakeRect( 0, 0, size.width, size.height );

        NSImage* image = [[NSImage alloc] initWithSize:size];
        [image lockFocus];
        [[NSColor whiteColor] set]; // We fill the rect with white, with full opacity, later on

        do
        {
                // Set up a temporary release pool so memory will get cleaned up properly
                NSAutoreleasePool *loopPool = [[NSAutoreleasePool alloc] init];

                NSRectFillUsingOperation( destinationRect, NSCompositeClear );
                [source drawInRect: destinationRect
                        fromRect: destinationRect
                        operation: NSCompositeCopy fraction: 1.0];

                NSBitmapImageRep* bitmap = [ [NSBitmapImageRep alloc]
                        initWithFocusedViewRect: destinationRect ];

                NSData* data = [bitmap representationUsingType:NSPNGFileType properties:nil];
                [bitmap release];

                [[NSFileManager defaultManager]
                        createFileAtPath: [ [NSString stringWithFormat: outputFileFormat, [sourcePath stringByDeletingPathExtension], page] stringByAppendingPathExtension: @"png"]
                        contents: data
                        attributes: nil ];

                if ( morePages == YES )
                {
                        // Go get the next page
                        if ( pdfSource != NULL && page < [pdfSource pageCount] )
                        {
                                [pdfSource setCurrentPage: page];
                                [source recache];
                                page ++;
                        }
                        else
                        {
                                morePages = NO;
                        }
                }

                [loopPool release];
        }
        while ( morePages == YES );

        [image unlockFocus];
        [image release];
        [pool release];
}