pdf2png.m

/* * complie
gcc --std=c99 -Wall -g -o pdf2png pdf2png.m -framework Cocoa
*/

#import <Cocoa/Cocoa.h>

static NSString* dumpPNG(CGPDFPageRef page, NSURL* outDir) {
    size_t num = CGPDFPageGetPageNumber(page);
    assert(num > 0);

    CGRect r = CGPDFPageGetBoxRect(page, kCGPDFTrimBox);

    // 解像度を72*4, 288dpiに設定
    size_t dpi = 72 * 4;
    size_t scale = dpi / 72;

    size_t w = r.size.width * scale;
    size_t h = r.size.height * scale;

    CGColorSpaceRef colorspace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
    CGContextRef ctx = CGBitmapContextCreate(
        NULL, // 10.6+
        w, h,
        8, w * 4,
        colorspace,
        kCGImageAlphaNoneSkipFirst
    );
    // CGColorSpaceRelease(colorspace);

    CGAffineTransform trans = CGAffineTransformMakeScale(scale, scale);
    CGContextConcatCTM(ctx, trans);

    //カラー作成
    CGFloat col[4];
    col[0] = 1.0;
    col[1] = 1.0;
    col[2] = 1.0;
    col[3] = 1.0;
    CGColorRef color = CGColorCreate(colorspace, col);
    //色空間の解放
    CGColorSpaceRelease(colorspace);
    
    CGContextSetFillColorWithColor(ctx, color);
  
    CGContextAddRect(ctx, CGRectMake(0.0, 0.0, w, h));
    CGContextFillPath(ctx);

    CGContextDrawPDFPage(ctx, page);
    CGImageRef img = CGBitmapContextCreateImage(ctx);
    assert(NULL != img);

    NSBitmapImageRep* rep = [[NSBitmapImageRep alloc] initWithCGImage:img];
    NSData* data = [rep representationUsingType:NSBitmapImageFileTypePNG properties:[NSDictionary dictionary]];
    [rep release];

    NSString* outFile = [[outDir path] stringByAppendingPathComponent:[NSString stringWithFormat:@"%04zu.png", num]];
    BOOL success = [data writeToFile:outFile atomically:NO];
    assert(YES == success);

    CGImageRelease(img);
    CGContextRelease(ctx);

    return outFile;
}

int main(int argc, char** argv) {
    NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];

    if (argc < 3) {
        NSLog(@"Usage: %s input.pdf output_dir\n", argv[0]);
        goto exit;
    }

    NSURL* inputFile = [NSURL fileURLWithPath:[NSString stringWithUTF8String:argv[1]]];
    NSURL* outputDir = [NSURL fileURLWithPath:[NSString stringWithUTF8String:argv[2]] isDirectory:YES];

    CGPDFDocumentRef pdf = CGPDFDocumentCreateWithURL((CFURLRef)inputFile);
    assert(NULL != pdf);

    size_t pages = CGPDFDocumentGetNumberOfPages(pdf);
    size_t p;
    for (p = 1; p <= pages; ++p) {
        NSAutoreleasePool* poolin = [[NSAutoreleasePool alloc] init];

        CGPDFPageRef page = CGPDFDocumentGetPage(pdf, p);
        assert(NULL != page);

        NSString* wrotePath = dumpPNG(page, outputDir);
        NSLog(@"wrote: %@", wrotePath);

        [poolin drain];
    }

    CGPDFDocumentRelease(pdf);
 exit:
    [pool drain];
    return 0;
}