Objective-C Requires Chilkat v11.7.0+

QR Code Error Correction Levels

See more QR Code Examples

Demonstrates the four QR error-correction levels. L, M, Q and H allow a reader to recover the data when about 7%, 15%, 25% and 30% of the symbol is damaged or covered. More error correction leaves less room for data, so the same text needs a larger symbol at a higher level. The default is M. The example also shows boostErrorCorrection, which raises the level for free when the chosen version has room to spare. Objective-C

#import <CkoFormats.h>
#import <CkoJsonObject.h>
#import <CkoJsonArray.h>

BOOL success = NO;

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

CkoFormats *fmt = [[CkoFormats alloc] init];
CkoJsonObject *json = [[CkoJsonObject alloc] init];
CkoJsonObject *jsonOut = [[CkoJsonObject alloc] init];
[json UpdateString: @"payload.text" value: @"https://www.chilkatsoft.com/barcode_overview.asp"];

//  Encode the same text at each level.
CkoJsonArray *levels = [[CkoJsonArray alloc] init];
[levels Load: @"[\"L\",\"M\",\"Q\",\"H\"]"];
int i;
for (i = 0; i <= 3; i++) {
    [json UpdateString: @"encoding.qr.errorCorrection" value: [levels StringAt: [NSNumber numberWithInt: i]]];
    success = [fmt QrCode: @"generate" jsonIn: json jsonOut: jsonOut];
    if (success == NO) {
        NSLog(@"%@",fmt.LastErrorText);
        return;
    }

    NSLog(@"%@%@%@%d%@%d%@",@"level ",[levels StringAt: [NSNumber numberWithInt: i]],@": version ",[[jsonOut IntOf: @"symbols[0].selectedEncoding.version"] intValue]
        ,@", ",[[jsonOut IntOf: @"symbols[0].dimensions.modulesWide"] intValue],@" modules wide");
}

//  The four symbols.  They hold the same text, and the higher the level, the larger the symbol:

//  

//  A symbol often has room left over.  boostErrorCorrection uses it: the level is raised
//  as far as the same version allows, so the symbol is no larger but is more robust.
CkoJsonObject *json2 = [[CkoJsonObject alloc] init];
[json2 UpdateString: @"payload.text" value: @"https://chilkatsoft.com"];
[json2 UpdateString: @"encoding.qr.errorCorrection" value: @"L"];
success = [fmt QrCode: @"generate" jsonIn: json2 jsonOut: jsonOut];
if (success == NO) {
    NSLog(@"%@",fmt.LastErrorText);
    return;
}

NSLog(@"%@%d%@%@",@"level L requested: version ",[[jsonOut IntOf: @"symbols[0].selectedEncoding.version"] intValue],@", level ",[jsonOut StringOf: @"symbols[0].selectedEncoding.errorCorrection"]);

[json2 UpdateBool: @"encoding.qr.boostErrorCorrection" value: YES];
success = [fmt QrCode: @"generate" jsonIn: json2 jsonOut: jsonOut];
if (success == NO) {
    NSLog(@"%@",fmt.LastErrorText);
    return;
}

NSLog(@"%@%d%@%@",@"level L with boost: version ",[[jsonOut IntOf: @"symbols[0].selectedEncoding.version"] intValue],@", level ",[jsonOut StringOf: @"symbols[0].selectedEncoding.errorCorrection"]);

//  Level L, and level M reached by the boost.  The two symbols are the same size:

//  

//  Sample output:

//  level L: version 3, 29 modules wide
//  level M: version 4, 33 modules wide
//  level Q: version 5, 37 modules wide
//  level H: version 6, 41 modules wide
//  level L requested: version 2, level L
//  level L with boost: version 2, level M