Objective-C Requires Chilkat v11.7.0+

Remove PDF Objects Nothing Refers To

See more PDF Optimization Examples

Demonstrates removeUnreferenced. When a page, an image or a whole section is replaced in an editor, the objects it used often stay in the file with nothing pointing at them any more. They are not old revisions -- they are in the current revision, simply unreachable -- so only a reachability walk from the document catalog finds them. In a publication assembled over several editing passes this is frequently the largest single saving. Objective-C

#import <CkoPdf.h>
#import <CkoJsonObject.h>

BOOL success = NO;

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

//  The PDF used in this example is available at watersense_accomplishments.pdf

CkoPdf *pdf = [[CkoPdf alloc] init];
success = [pdf LoadFile: @"qa_data/pdf/watersense_accomplishments.pdf"];
if (success == NO) {
    NSLog(@"%@",pdf.LastErrorText);
    return;
}

CkoJsonObject *json = [[CkoJsonObject alloc] init];
CkoJsonObject *jsonOut = [[CkoJsonObject alloc] init];
success = [pdf Optimize: @"audit" jsonIn: json jsonOut: jsonOut];
if (success == NO) {
    NSLog(@"%@",pdf.LastErrorText);
    return;
}

NSLog(@"%@%d",@"fileSize: ",[[jsonOut IntOf: @"fileSize"] intValue]);
NSLog(@"%@%d",@"removeUnreferenced would save: ",[[jsonOut IntOf: @"estimatedSavings.removeUnreferenced"] intValue]);

//  Optimize with the defaults and see how many objects were actually dropped.
success = [pdf Optimize: @"optimize" jsonIn: json jsonOut: jsonOut];
if (success == NO) {
    NSLog(@"%@",pdf.LastErrorText);
    return;
}

success = [pdf WriteFile: @"qa_output/watersense_optimized.pdf"];
if (success == NO) {
    NSLog(@"%@",pdf.LastErrorText);
    return;
}

NSLog(@"%@%d",@"objects removed: ",[[jsonOut IntOf: @"actions.removeUnreferenced.count"] intValue]);
NSLog(@"%@%d",@"bytes saved:     ",[[jsonOut IntOf: @"actions.removeUnreferenced.bytesSaved"] intValue]);

//  Nothing a page needs is ever removed: the walk starts at the document catalog and follows every
//  reference, including the ones in annotations, the structure tree, named destinations and the
//  optional-content configuration.
NSLog(@"%@%d",@"pages after: ",[pdf.NumPages intValue]);