Add a new class, QRImageView, which displaying QR code in it.

QRCodeEncoderDemo/QRCodeEncoderDemoViewController.h

@@ -7,6 +7,7 @@
 #import <UIKit/UIKit.h>
 #import "QREncoder.h"
 #import "DataMatrix.h"
+#import "QRImageView.h"
 
 @interface QRCodeEncoderDemoViewController : UIViewController {
 

QRCodeEncoderDemo/QRCodeEncoderDemoViewController.mm

@@ -16,6 +16,7 @@ - (void)viewDidLoad
 {
     [super viewDidLoad];
 
+    UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:self.view.frame];
 
     //the qrcode is square. now we make it 250 pixels wide
     int qrcodeImageDimension = 250;
@@ -32,17 +33,31 @@ - (void)viewDidLoad
     //put the image into the view
     UIImageView* qrcodeImageView = [[UIImageView alloc] initWithImage:qrcodeImage];
     CGRect parentFrame = self.view.frame;
-    CGRect tabBarFrame = self.tabBarController.tabBar.frame;
 
-    //center the image
-    CGFloat x = (parentFrame.size.width - qrcodeImageDimension) / 2.0;
-    CGFloat y = (parentFrame.size.height - qrcodeImageDimension - tabBarFrame.size.height) / 2.0;
-    CGRect qrcodeImageViewFrame = CGRectMake(x, y, qrcodeImageDimension, qrcodeImageDimension);
+    //put the image on a scroll view
+    CGFloat margin = (parentFrame.size.width - qrcodeImageDimension) / 2.0;
+    CGRect qrcodeImageViewFrame = CGRectMake(margin, margin, qrcodeImageDimension, qrcodeImageDimension);
     [qrcodeImageView setFrame:qrcodeImageViewFrame];
 
-    //and that's it!
-    [self.view addSubview:qrcodeImageView];
+    //you can also show the matrix using QRImageView
+    CGRect qrcodeImageViewFrame2 = CGRectMake(margin, margin * 2 + qrcodeImageDimension, qrcodeImageDimension, qrcodeImageDimension);
+    QRImageView* qrcodeImageView2 = [[QRImageView alloc] initWithFrame:qrcodeImageViewFrame2];
+
+    //you can set the border arounding the QR code to make scanning easier, the default with is 4 dots
+    qrcodeImageView2.borderWidth = 4;
+
+    //assign the matrix
+    qrcodeImageView2.dataMatrix = qrMatrix;
+
+    //and that's it! The upper one is a bitmap image shown in UIImageView, the lower one is a QRImageView showing the same data matrix.
+    [scrollView addSubview:qrcodeImageView];
+    [scrollView addSubview:qrcodeImageView2];
+    [scrollView setContentSize:CGSizeMake(parentFrame.size.width, qrcodeImageDimension * 2 + margin * 3)];
+    [self.view addSubview:scrollView];
+
     [qrcodeImageView release];
+    [qrcodeImageView2 release];
+    [scrollView release];
 }
 
 @end

QRCodeEncoderObjectiveCAtGithub.xcodeproj/project.pbxproj

@@ -7,6 +7,8 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		5889BAAF17709DD100C7697A /* QRImageView.h in Headers */ = {isa = PBXBuildFile; fileRef = 5889BAAD17709DD100C7697A /* QRImageView.h */; };
+		5889BAB017709DD100C7697A /* QRImageView.m in Sources */ = {isa = PBXBuildFile; fileRef = 5889BAAE17709DD100C7697A /* QRImageView.m */; };
 		9621844415431DBA00447877 /* UIKit.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 9621844315431DBA00447877 /* UIKit.framework */; };
 		9621844515431DBA00447877 /* Foundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 9672D35A13BD662F0002B0E2 /* Foundation.framework */; };
 		9621844715431DBA00447877 /* CoreGraphics.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 9621844615431DBA00447877 /* CoreGraphics.framework */; };
@@ -38,6 +40,8 @@
 /* End PBXContainerItemProxy section */
 
 /* Begin PBXFileReference section */
+		5889BAAD17709DD100C7697A /* QRImageView.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = QRImageView.h; sourceTree = "<group>"; };
+		5889BAAE17709DD100C7697A /* QRImageView.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = QRImageView.m; sourceTree = "<group>"; };
 		9621844115431DBA00447877 /* QRCodeEncoderDemo.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = QRCodeEncoderDemo.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		9621844315431DBA00447877 /* UIKit.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = UIKit.framework; path = System/Library/Frameworks/UIKit.framework; sourceTree = SDKROOT; };
 		9621844615431DBA00447877 /* CoreGraphics.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = CoreGraphics.framework; path = System/Library/Frameworks/CoreGraphics.framework; sourceTree = SDKROOT; };
@@ -148,6 +152,8 @@
 				9672D36813BD665E0002B0E2 /* QREncoder-Prefix.pch */,
 				9672D36913BD665E0002B0E2 /* QREncoder.h */,
 				9672D36A13BD665E0002B0E2 /* QREncoder.mm */,
+				5889BAAD17709DD100C7697A /* QRImageView.h */,
+				5889BAAE17709DD100C7697A /* QRImageView.m */,
 				9672D35D13BD662F0002B0E2 /* Supporting Files */,
 			);
 			path = QRCodeEncoderObjectiveCAtGithub;
@@ -173,6 +179,7 @@
 				9672D36E13BD665E0002B0E2 /* QR_Encode.h in Headers */,
 				9672D36F13BD665E0002B0E2 /* QREncoder-Prefix.pch in Headers */,
 				BA7984CF1043BDE62FC71866 /* QRCodeEncoderDemoViewController.h in Headers */,
+				5889BAAF17709DD100C7697A /* QRImageView.h in Headers */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -270,6 +277,7 @@
 				9672D36D13BD665E0002B0E2 /* QR_Encode.cpp in Sources */,
 				9672D37113BD665E0002B0E2 /* QREncoder.mm in Sources */,
 				BA798313F4E3F133E55601A3 /* QRCodeEncoderDemoViewController.mm in Sources */,
+				5889BAB017709DD100C7697A /* QRImageView.m in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

QRCodeEncoderObjectiveCAtGithub/DataMatrix.mm

@@ -6,7 +6,7 @@
 @implementation DataMatrix
 
 - (id)initWith:(int)dimension {
-    if ([super init]) {
+    if (self = [super init]) {
         self->dim = dimension;
         self->data = (bool**)malloc(sizeof(bool*) * self->dim);
         for (int y=0; y<self->dim; y++) {

QRCodeEncoderObjectiveCAtGithub/QRImageView.h

@@ -0,0 +1,17 @@
+//
+//  QRImageView.h
+//  QRCodeEncoderObjectiveCAtGithub
+//
+//  Created by Shiva Huang on 13/6/18.
+//
+//
+
+#import <UIKit/UIKit.h>
+#import "DataMatrix.h"
+
+@interface QRImageView : UIView
+
+@property (strong, nonatomic) DataMatrix *dataMatrix;
+@property (assign, nonatomic) unsigned int borderWidth;
+
+@end

QRCodeEncoderObjectiveCAtGithub/QRImageView.m

@@ -0,0 +1,64 @@
+//
+//  QRImageView.m
+//  QRCodeEncoderObjectiveCAtGithub
+//
+//  Created by Shiva Huang on 13/6/18.
+//
+//
+
+#import "QRImageView.h"
+
+@implementation QRImageView
+
+- (id)initWithFrame:(CGRect)frame
+{
+    self = [super initWithFrame:frame];
+    if (self) {
+        // Initialization code
+        self.borderWidth = 4;
+    }
+    return self;
+}
+
+
+// Only override drawRect: if you perform custom drawing.
+// An empty implementation adversely affects performance during animation.
+- (void)drawRect:(CGRect)rect
+{
+    CGContextRef context = UIGraphicsGetCurrentContext();
+
+    CGContextSetFillColorWithColor(context, [self.backgroundColor CGColor]);
+    CGContextFillRect(context, rect);
+
+    if(self.dataMatrix == nil)
+        return;
+
+    const int dataDimension = self.dataMatrix.dimension;
+    const CGFloat imageDimension = MIN(self.frame.size.width, self.frame.size.height);
+    const CGFloat pixelPerDot = imageDimension / (dataDimension + self.borderWidth * 2);
+    CGFloat yMargin = (self.frame.size.height - imageDimension) / 2.0;
+    CGFloat xMargin = (self.frame.size.width - imageDimension) / 2.0;
+    CGFloat yOffset = 0.0;
+
+    // Drawing code
+    CGContextSetFillColorWithColor(context, [[UIColor whiteColor] CGColor]);
+    CGContextFillRect(context, CGRectMake(xMargin, yMargin, imageDimension, imageDimension));
+
+    CGContextSetFillColorWithColor(context, [[UIColor blackColor] CGColor]);
+    yMargin += self.borderWidth * pixelPerDot;
+    xMargin += self.borderWidth * pixelPerDot;
+
+    for(int my=0; my<dataDimension; my++) {
+        yOffset = yMargin + my * pixelPerDot;
+
+        for(int mx=0; mx<dataDimension; mx++) {
+            if([self.dataMatrix valueAt:mx y:my]) {
+                CGContextAddRect(context, CGRectMake(xMargin + mx * pixelPerDot, yOffset, pixelPerDot, pixelPerDot));
+            }
+        }
+    }
+
+    CGContextFillPath(context);
+}
+
+@end