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 <ejones@uwaterloo.ca> Februrary, 2004
// http://www.eng.uwaterloo.ca/~ejones/
//
// Released under the "do whatever you want" public domain licence.

#include <objc/objc.h>
#include <Cocoa/Cocoa.h>

int main( int argc, char* argv[] )
{
    double 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 )
    {
        // 2006/08/28 21:18  use stringWithUTF8String
        // [args addObject: [NSString stringWithCString: argv[i]] ];
        [args addObject: [NSString stringWithUTF8String: argv[i]] ];
    }
    
    // If we have a "--dpi" along with a corresponding argument ...
    NSUInteger index = NSNotFound;
    if ( (index = [args indexOfObject: @"--dpi"]) != NSNotFound && index + 1 < [args count] )
    {
        // Parse it as an integer
        desiredResolution = [[args objectAtIndex: index + 1] doubleValue];
        [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];
    }
    
    // --transparent    Do not fill background white color, keep transparency from PDF.
    BOOL keepTransparent = NO;
    if ( (index = [args indexOfObject: @"--transparent"]) != NSNotFound )
    {
        keepTransparent = YES;
        [args removeObjectAtIndex: index];
    }
    
    // If we have a "--output" along with a corresponding argument ...
    NSString *explicitOutputFilePath;
    if ( (index = [args indexOfObject: @"--output"]) != NSNotFound && index + 1 < [args count] )
    {
        explicitOutputFilePath = [args objectAtIndex: index + 1];
        morePages = NO; // only output single page
        [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--transparent\tDo not fill background white color, keep transparency from PDF.\n" );
        fprintf( stderr, "\t--output path\tSpecify output file path. This implies --page 1 if not specified. ( Without this option, PDFNAME-p1.png (example) is created on same directory )\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: @"%ld", (long)[pdfSource pageCount]] length];
            outputFileFormat = [NSString stringWithFormat: @"%%@-p%%0%dd", numDigits];
        }
    }
    
    
    [NSApplication sharedApplication];
    [[NSGraphicsContext currentContext] setImageInterpolation: NSImageInterpolationHigh];
    
    
    do
    {
        // Set up a temporary release pool so memory will get cleaned up properly
        NSAutoreleasePool *loopPool = [[NSAutoreleasePool alloc] init];
        
        
        NSSize sourceSize = [pdfSource 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 );
        
        //	[source setSize: size];
        NSRect sourceRect = NSMakeRect( 0, 0, sourceSize.width, sourceSize.height );
        NSRect destinationRect = NSMakeRect( 0, 0, size.width, size.height );
        
        NSImage* image = [[NSImage alloc] initWithSize:size];
        [image lockFocus];
        
        
        if (keepTransparent) {
            [pdfSource drawInRect: destinationRect
                         fromRect: sourceRect
                        operation: NSCompositeCopy fraction: 1.0 respectFlipped: NO hints: [NSDictionary dictionary] ];
        } else {
            [[NSColor whiteColor] set];
            NSRectFill( destinationRect );
            [pdfSource drawInRect: destinationRect
                         fromRect: sourceRect
                        operation: NSCompositeSourceOver fraction: 1.0 respectFlipped: NO hints: [NSDictionary dictionary] ];
        }
        
        NSBitmapImageRep* bitmap = [ [NSBitmapImageRep alloc]
                                    initWithFocusedViewRect: destinationRect ];
        
        NSData* data = [bitmap representationUsingType:NSPNGFileType properties:nil];
        [bitmap release];
        
        NSString *outputFilePath = NULL;
        if (explicitOutputFilePath == NULL) {
            outputFilePath = [ [NSString stringWithFormat: outputFileFormat, [sourcePath stringByDeletingPathExtension], page] stringByAppendingPathExtension: @"png"];
        } else {
            outputFilePath = explicitOutputFilePath;
        }
        
        [[NSFileManager defaultManager]
         createFileAtPath: outputFilePath
         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;
            }
        }
        
        [image unlockFocus];
        [image release];
        [loopPool release];
    }
    while ( morePages == YES );
    
    [pool release];
}