ios OpenCV增加图像大小

ios OpenCV increases the image size

本文关键字：图像 增加 OpenCV ios      更新时间：2023-10-16

下面是将UIImage转换为cv::Mat的代码

+ (cv::Mat)cvMatFromUIImage:(UIImage *)image {
    CGColorSpaceRef colorSpace = CGImageGetColorSpace(image.CGImage);
    CGFloat cols, rows;
    if (image.imageOrientation == UIImageOrientationLeft || image.imageOrientation == UIImageOrientationRight) {
        cols = image.size.height;
        rows = image.size.width;
    } else {
        cols = image.size.width;
        rows = image.size.height;
    }
    cv::Mat cvMat(rows, cols, CV_8UC4); // 8 bits per component, 4 channels    
    CGContextRef contextRef = CGBitmapContextCreate(cvMat.data,             // Pointer to backing data
                                                cols,                       // Width of bitmap
                                                rows,                       // Height of bitmap
                                                8,                          // Bits per component
                                                cvMat.step[0],              // Bytes per row
                                                colorSpace,                 // Colorspace
                                                kCGImageAlphaNoneSkipLast |
                                                kCGBitmapByteOrderDefault);
    CGContextDrawImage(contextRef, CGRectMake(0, 0, cols, rows), image.CGImage);
    CGContextRelease(contextRef);
    cv::Mat cvMatTest;
    cv::transpose(cvMat, cvMatTest);
    if (image.imageOrientation == UIImageOrientationLeft || image.imageOrientation == UIImageOrientationRight) {
    } else {
        return cvMat;       
    }
    cvMat.release();    
    cv::flip(cvMatTest, cvMatTest, 1);
    return cvMatTest;
}

cv::Mat到UIImage的代码

+ (UIImage *)UIImageFromCVMat:(cv::Mat)cvMat {
    NSData *data = [NSData dataWithBytes:cvMat.data length:cvMat.elemSize() * cvMat.total()];    
    CGColorSpaceRef colorSpace;
    if (cvMat.elemSize() == 1) {
        colorSpace = CGColorSpaceCreateDeviceGray();
    } else {
        colorSpace = CGColorSpaceCreateDeviceRGB();
    }
    CGDataProviderRef provider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data);
    CGImageRef imageRef = CGImageCreate(cvMat.cols,                                     // Width
                                    cvMat.rows,                                     // Height
                                    8,                                              // Bits per component
                                    8 * cvMat.elemSize(),                           // Bits per pixel
                                    cvMat.step[0],                                  // Bytes per row
                                    colorSpace,                                     // Colorspace
                                    kCGImageAlphaNone | kCGBitmapByteOrderDefault,  // Bitmap info flags
                                    provider,                                       // CGDataProviderRef
                                    NULL,                                           // Decode
                                    false,                                          // Should interpolate
                                    kCGRenderingIntentDefault);                     // Intent
    UIImage *image = [[UIImage alloc] initWithCGImage:imageRef];
    CGImageRelease(imageRef);
    CGDataProviderRelease(provider);
    CGColorSpaceRelease(colorSpace);    
    return image;
}

我将1080*1920 (1.5 mb)的图像转换为cv::Mat，经过一些预处理后，我将其转换为UIImage，这给了我2517 * 1527(6 mb)的图像

即使经过图像处理，我也不想增加图像大小。请告诉我哪里做错了

作物行动

//

 cv::Mat undistorted = cv::Mat( cvSize(maxWidth,maxHeight), CV_8UC4);
cv::Mat original = [MMOpenCVHelper cvMatFromUIImage:_adjustedImage];

cv::warpPerspective(original, undistorted, cv::getPerspectiveTransform(src, dst), cvSize(maxWidth, maxHeight));

您的代码没有调整图像的大小。这一定是预处理的一个意想不到的副作用，你在这里没有详细说明。

 UIImage* image = self.testImage;
 NSLog(@"original UIImage: %.0f %.0f", image.size.width,image.size.height);
 cv::Mat matImage = [self cvMatFromUIImage:image];
 NSLog(@"cv matImage: %d %d", matImage.cols,matImage.rows);
 UIImage* newImage = [self UIImageFromCVMat:matImage];
 NSLog(@"new UIImage: %.0f %.0f", newImage.size.width,newImage.size.height);

original UIImage: 720 960
     cv matImage: 720 960
     new UIImage: 720 960

编辑
根据您的扩展问题，看起来warpPerspective的输出大小为cvSize(maxWidth,maxHeight) -这就是您将获得的大小。如果您想以输入大小结束，可以先转换为resize()，然后再转换回UIImage。或者直接将输出mat设置为与输入相同的大小。

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