Question

我正在使用UIViewContentModeScaleToFill缩放图片。缩放后，图片没有显示在正确的位置。帮助我。

以下是我的代码：

  UIImage *image=[UIImage imageNamed:@"image2.png"];
    UIImageView *imageView = [[UIImageView alloc] initWithImage:image]; 
    imageView.frame=CGRectMake(0, 0, 200, 200);
    imageView.contentMode = UIViewContentModeScaleAspectFit;

    //change width of frame
    CGRect frame = imageView.frame;
    imageView.frame = frame;
    [self.view addSubview:imageView];

缩放后：

参考图片1

缩放前：

参考图片2

我想从原点（0,0）开始缩放图像。

Answer 1

首先，你的代码中有UIViewContentModeScaleAspectFit，而不是你所说的UIViewContentModeScaleToFill。请发布原始图片。
其次，“框架的更改宽度”部分无用，imageView.size.width已设置为200。缩放模式根本不会改变视图的框架，它们会改变显示其内容的方式。

我不知道你所谈论的'正确位置'是什么，但试着像这样imageView全屏：

UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
imageView.contentMode = UIViewContentModeScaleToFill;
imageView.frame = self.view.frame;

Answer 2

您好，请尝试下面的代码，希望它可以帮助您了解....

 UIImage *image=[UIImage imageNamed:@"image2.png"];
    UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
  //  imageView.contentMode = UIViewContentModeScaleToFill;
    imageView.contentMode = UIViewContentModeScaleAspectFit; 
    imageView.frame = self.view.bounds;
    [self.view addSubview:imageView];

以下评论后更新：

我想裁剪图像而不改变其宽高比。宽度是200px。高度将根据宽度而变化。 - shivam

您想裁剪意味着您尝试以下类别代码：

<强>的UIImage + MyImage.h

#import <UIKit/UIKit.h>

@interface UIImage (MyImage)


+ (UIImage*)imageFromView:(UIView*)view;
+ (UIImage*)imageFromView:(UIView*)view scaledToSize:(CGSize)newSize;
+ (UIImage*)imageWithImage:(UIImage*)image scaledToSize:(CGSize)newSize;
+ (void)beginImageContextWithSize:(CGSize)size;
+ (UIImage *)croppedImage:(UIImage *)myImage :(CGRect)bounds;

+ (UIImage *) imageFromColor:(UIColor *)color;

@end

<强>的UIImage + MyImage.m

#import "UIImage+MyImage.h"

@implementation UIImage (MyImage)

+ (void)beginImageContextWithSize:(CGSize)size
{
    if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)]) {
        if ([[UIScreen mainScreen] scale] == 2.0) {
            UIGraphicsBeginImageContextWithOptions(size, YES, 2.0);
        } else {
            UIGraphicsBeginImageContext(size);
        }
    } else {
        UIGraphicsBeginImageContext(size);
    }
}

+ (void)endImageContext
{
    UIGraphicsEndImageContext();
}

+ (UIImage*)imageFromView:(UIView*)view
{
    [self beginImageContextWithSize:[view bounds].size];
    BOOL hidden = [view isHidden];
    [view setHidden:NO];
    [[view layer] renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    [self endImageContext];
    [view setHidden:hidden];
    return image;
}

+ (UIImage*)imageFromView:(UIView*)view scaledToSize:(CGSize)newSize
{
    UIImage *image = [self imageFromView:view];
    if ([view bounds].size.width != newSize.width ||
        [view bounds].size.height != newSize.height) {
        image = [self imageWithImage:image scaledToSize:newSize];
    }
    return image;
}

+ (UIImage*)imageWithImage:(UIImage*)image scaledToSize:(CGSize)newSize
{
    [self beginImageContextWithSize:newSize];
    [image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    [self endImageContext];
    return newImage;
}


+ (UIImage *)croppedImage:(UIImage *)myImage :(CGRect)bounds {
    CGImageRef imageRef = CGImageCreateWithImageInRect(myImage.CGImage, bounds);
    UIImage *croppedImage = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
    CGSize asd =  croppedImage.size;
    return croppedImage;
}





+ (UIImage *) imageFromColor:(UIColor *)color {
    CGRect rect = CGRectMake(0, 0, 1, 1);
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, [color CGColor]);
    //  [[UIColor colorWithRed:222./255 green:227./255 blue: 229./255 alpha:1] CGColor]) ;
    CGContextFillRect(context, rect);
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return img;
}




@end

电话会是：

imageView.image=[UIImage croppedImage:imageView.Image :CGRectMake(0,0,200,200) ];

Answer 3

您可以使用此代码修复不需要的旋转图像

Swift 5 扩展：

extension UIImage {
    /// Fix image orientaton to protrait up
    func fixedOrientation() -> UIImage? {
        guard imageOrientation != UIImage.Orientation.up else {
            // This is default orientation, don't need to do anything
            return self.copy() as? UIImage
        }

        guard let cgImage = self.cgImage else {
            // CGImage is not available
            return nil
        }

        guard let colorSpace = cgImage.colorSpace, let ctx = CGContext(data: nil, width: Int(size.width), height: Int(size.height), bitsPerComponent: cgImage.bitsPerComponent, bytesPerRow: 0, space: colorSpace, bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue) else {
            return nil // Not able to create CGContext
        }

        var transform: CGAffineTransform = CGAffineTransform.identity

        switch imageOrientation {
        case .down, .downMirrored:
            transform = transform.translatedBy(x: size.width, y: size.height)
            transform = transform.rotated(by: CGFloat.pi)
        case .left, .leftMirrored:
            transform = transform.translatedBy(x: size.width, y: 0)
            transform = transform.rotated(by: CGFloat.pi / 2.0)
        case .right, .rightMirrored:
            transform = transform.translatedBy(x: 0, y: size.height)
            transform = transform.rotated(by: CGFloat.pi / -2.0)
        case .up, .upMirrored:
            break
        @unknown default:
            fatalError("Missing...")
            break
        }

        // Flip image one more time if needed to, this is to prevent flipped image
        switch imageOrientation {
        case .upMirrored, .downMirrored:
            transform = transform.translatedBy(x: size.width, y: 0)
            transform = transform.scaledBy(x: -1, y: 1)
        case .leftMirrored, .rightMirrored:
            transform = transform.translatedBy(x: size.height, y: 0)
            transform = transform.scaledBy(x: -1, y: 1)
        case .up, .down, .left, .right:
            break
        @unknown default:
            fatalError("Missing...")
            break
        }

        ctx.concatenate(transform)

        switch imageOrientation {
        case .left, .leftMirrored, .right, .rightMirrored:
            ctx.draw(cgImage, in: CGRect(x: 0, y: 0, width: size.height, height: size.width))
        default:
            ctx.draw(cgImage, in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
            break
        }

        guard let newCGImage = ctx.makeImage() else { return nil }
        return UIImage.init(cgImage: newCGImage, scale: 1, orientation: .up)
    }
}

目标 C 代码：

-(UIImage *)scaleAndRotateImage:(UIImage *)image{
        // No-op if the orientation is already correct
        if (image.imageOrientation == UIImageOrientationUp) return image;
        
        // We need to calculate the proper transformation to make the image upright.
        // We do it in 2 steps: Rotate if Left/Right/Down, and then flip if Mirrored.
        CGAffineTransform transform = CGAffineTransformIdentity;
        
        switch (image.imageOrientation) {
            case UIImageOrientationDown:
            case UIImageOrientationDownMirrored:
                transform = CGAffineTransformTranslate(transform, image.size.width, image.size.height);
                transform = CGAffineTransformRotate(transform, M_PI);
                break;
                
            case UIImageOrientationLeft:
            case UIImageOrientationLeftMirrored:
                transform = CGAffineTransformTranslate(transform, image.size.width, 0);
                transform = CGAffineTransformRotate(transform, M_PI_2);
                break;
                
            case UIImageOrientationRight:
            case UIImageOrientationRightMirrored:
                transform = CGAffineTransformTranslate(transform, 0, image.size.height);
                transform = CGAffineTransformRotate(transform, -M_PI_2);
                break;
            case UIImageOrientationUp:
            case UIImageOrientationUpMirrored:
                break;
        }
        
        switch (image.imageOrientation) {
            case UIImageOrientationUpMirrored:
            case UIImageOrientationDownMirrored:
                transform = CGAffineTransformTranslate(transform, image.size.width, 0);
                transform = CGAffineTransformScale(transform, -1, 1);
                break;
                
            case UIImageOrientationLeftMirrored:
            case UIImageOrientationRightMirrored:
                transform = CGAffineTransformTranslate(transform, image.size.height, 0);
                transform = CGAffineTransformScale(transform, -1, 1);
                break;
            case UIImageOrientationUp:
            case UIImageOrientationDown:
            case UIImageOrientationLeft:
            case UIImageOrientationRight:
                break;
        }
        
        // Now we draw the underlying CGImage into a new context, applying the transform
        // calculated above.
        CGContextRef ctx = CGBitmapContextCreate(NULL, image.size.width, image.size.height,
                                                 CGImageGetBitsPerComponent(image.CGImage), 0,
                                                 CGImageGetColorSpace(image.CGImage),
                                                 CGImageGetBitmapInfo(image.CGImage));
        CGContextConcatCTM(ctx, transform);
        switch (image.imageOrientation) {
            case UIImageOrientationLeft:
            case UIImageOrientationLeftMirrored:
            case UIImageOrientationRight:
            case UIImageOrientationRightMirrored:
                // Grr...
                CGContextDrawImage(ctx, CGRectMake(0,0,image.size.height,image.size.width), image.CGImage);
                break;
                
            default:
                CGContextDrawImage(ctx, CGRectMake(0,0,image.size.width,image.size.height), image.CGImage);
                break;
        }
        
        // And now we just create a new UIImage from the drawing context
        CGImageRef cgimg = CGBitmapContextCreateImage(ctx);
        UIImage *img = [UIImage imageWithCGImage:cgimg];
        CGContextRelease(ctx);
        CGImageRelease(cgimg);
        return img;
}

代码的使用

 UIImage *img=[info objectForKey:UIImagePickerControllerOriginalImage];

 img=[self scaleAndRotateImage:img];
 NSData *image = UIImageJPEGRepresentation(img, 0.1);

缩放后图像位置不正确

3 个答案: