圖形辨識小程式

圖形辨識

UIImage+HTWDetector.h 辨識圖片的擴充

將可以用的辨識集合成enum

typedef NS_ENUM(NSUInteger, HTWFeatureType) {
    HTWFeatureTypeFace,         //人臉
    HTWFeatureTypeRectangle,    //矩型
    HTWFeatureTypeQRCode,       //QRCode
    HTWFeatureTypeText,         //文字
};

圖形辨識步驟:

• 建立原生辨識元件

	CIDetector *detector = [CIDetector detectorOfType:[self featureWithType:type] context:nil options:@{CIDetectorAccuracy:CIDetectorAccuracyHigh}];

• 將UIImage轉換為CIImage

	CIImage *image = [[CIImage alloc] initWithImage:self];

• 其實就是這一行指令在作圖形辨識(這會很花時間喔)

	NSArray *features = [detector featuresInImage:image];

這個小範例就是將這3個步驟封裝成一個category

提供的method如下

/*
辨識圖片
 type:辨識的種類
 block:辨識完成後回傳
 */
-(void)featureOfType:(HTWFeatureType)type block:(void(^ _Nullable)(NSArray<CIFeature *> * _Nonnull features,CIImage * _Nonnull cimage))block;

---

範例

首先當然是先載入cateogry，並建立使用的圖片

#import "UIImage+HTWDetector.h"
…
UIImage *temp = [UIImage imageNamed:@"star4"];	//載入圖片

• CIDetectorTypeFace 人臉辨識

[temp featureOfType:HTWFeatureTypeFace block:^(NSArray<CIFeature *> * _Nonnull features,CIImage *ciimage) {
	//辨識後要處理的事情
    …
}];

• CIDetectorTypeRectangle 矩形辨識

[temp featureOfType:HTWFeatureTypeRectangle block:^(NSArray<CIFeature *> * _Nonnull features,CIImage *ciimage) {
	//辨識後要處理的事情
    …
}];

• CIDetectorTypeQRCode QRCode辨識與產生

[temp featureOfType:HTWFeatureTypeQRCode block:^(NSArray<CIFeature *> * _Nonnull features,CIImage *ciimage) {
	//辨識後要處理的事情
    …
}];

• CIDetectorTypeText 文字辨識

[temp featureOfType:HTWFeatureTypeText block:^(NSArray<CIFeature *> * _Nonnull features,CIImage *ciimage) {
	//辨識後要處理的事情
    …
}];

## 座標轉換 `UIImage+HTWDetector.h` CIImage 座標轉換為 UIImageView 的對應座標 由於CIImage的座標與UIImageView的座標是上下相反，需要轉換，所以對`CIImage`擴充了一個`category`，新增`property` ```objectivec //CIImage座標轉換UIImage @property(nonatomic,readonly) CGAffineTransform toImageTransform; ``` 實作方法為: ```objectivec //取得圖片大小 CGSize ciImageSize = self.extent.size; //上下相反 CGAffineTransform transform = CGAffineTransformMakeScale(1, -1); //對y軸作延伸，長度為原圖高度 transform = CGAffineTransformTranslate(transform, 0, -ciImageSize.height); return transform; ``` 只有這樣還不夠，還需要實際呈現的view才行 `CIFeature+HTWTransform.h` 新增兩個方法: ```objectivec /* 取得在UIImageView的相對區塊 image:原始的圖片 view:父層的UIImageView */ -(CGRect)rightBoundsWithSourceImage:(CIImage *)image superView:(UIImageView *)view;

/* 取得在UIImageView的相對座標 point:座標 image:原始的圖片 view:父層的UIImageView */ -(CGPoint)rightPointWithPoint:(CGPoint)point sourceImage:(CIImage *)image superView:(UIImageView *)view;

實作方法為:
```objectivec
-(CGRect)rightBoundsWithSourceImage:(CIImage *)image superView:(UIImageView *)view
{
    //CIImage座標與UIImage座標的轉換
    CGAffineTransform transform = image.toImageTransform;

    //CIImage辨識區塊的邊界
    CGRect bounds = self.bounds;

    //轉換為UIImage辨識區塊的邊界
    CGRect faceBounds = CGRectApplyAffineTransform(bounds,transform);

    //依父層imageView大小調整邊界的比例
    CGSize viewSize = view.bounds.size;
    CGSize ciImageSize = image.extent.size;
    //取得比例
    CGFloat scale = MIN(viewSize.width / ciImageSize.width,
                        viewSize.height / ciImageSize.height);
    //取得x座標偏移
    CGFloat offsetX = (viewSize.width - ciImageSize.width * scale) / 2;
    //取得y座標偏移
    CGFloat offsetY = (viewSize.height - ciImageSize.height * scale) / 2;

    //調整比例
    faceBounds = CGRectApplyAffineTransform(faceBounds,CGAffineTransformMakeScale(scale, scale));
    //座標偏移
    faceBounds.origin.x += offsetX;
    faceBounds.origin.y += offsetY;

    return faceBounds;
}

---

範例 - QRCode

首先當然是先載入cateogry，再辨識完QRCode後使用

#import "CIFeature+HTWTransform.h"
…
for (CIQRCodeFeature *feature in features) {
	//取得正確座標
    CGRect bounds = [feature rightBoundsWithSourceImage:ciimage superView:self.mainImageView];
    //依座標建立一個有紅框的view
    UIView *view = [[UIView alloc] initWithFrame:bounds];
    view.layer.borderColor = [UIColor redColor].CGColor;
    view.layer.borderWidth = 1;
    [self.mainImageView addSubview:view];

    //建立QRCode
    [tempArray addObject:[UIImage createImageWithQRCode:feature.messageString length:100]];
}