UIImageView适配宽度

Question

我有一个安装在UIScrollView中的UIImageView。图像视图中的图像比iPhone的屏幕要大。我想要做的是让图像按比例缩放以适应屏幕的宽度，而不改变图像的纵横比(图像的一部分将在底部的屏幕外)。

我尝试过使用UIViewContentModeScaleAspectFill和UIViewContentModeScaleAspectFit，但它们都不能满足我的需要。

有什么想法吗？

谢谢。

Answer 1

这是我写的一个图像类，用来做一些类似这样的简单函数，fitInsideWidth是应该在这里应用的函数：

MyImage.h

#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>

@interface MyImage : NSObject

+ (UIImage*)imageWithImage:(UIImage *)image convertToWidth:(float)width covertToHeight:(float)height;
+ (UIImage*)imageWithImage:(UIImage *)image convertToHeight:(float)height;
+ (UIImage*)imageWithImage:(UIImage *)image convertToWidth:(float)width;
+ (UIImage*)imageWithImage:(UIImage *)image fitInsideWidth:(float)width fitInsideHeight:(float)height;
+ (UIImage*)imageWithImage:(UIImage *)image fitOutsideWidth:(float)width fitOutsideHeight:(float)height;
+ (UIImage*)imageWithImage:(UIImage *)image cropToWidth:(float)width cropToHeight:(float)height;

@end

MyImage.m

#import "MyImage.h"

@implementation MyImage

+ (UIImage*)imageWithImage:(UIImage *)image convertToWidth:(float)width covertToHeight:(float)height {
    CGSize size = CGSizeMake(width, height);
    UIGraphicsBeginImageContext(size);
    [image drawInRect:CGRectMake(0, 0, size.width, size.height)];
    UIImage * newimage = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();
    return newimage;
}

+ (UIImage*)imageWithImage:(UIImage *)image convertToHeight:(float)height {
    float ratio = image.size.height / height;
    float width = image.size.width / ratio;
    CGSize size = CGSizeMake(width, height);
    UIGraphicsBeginImageContext(size);
    [image drawInRect:CGRectMake(0, 0, size.width, size.height)];
    UIImage * newimage = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();
    return newimage;
}

+ (UIImage*)imageWithImage:(UIImage *)image convertToWidth:(float)width {
    float ratio = image.size.width / width;
    float height = image.size.height / ratio;
    CGSize size = CGSizeMake(width, height);
    UIGraphicsBeginImageContext(size);
    [image drawInRect:CGRectMake(0, 0, size.width, size.height)];
    UIImage * newimage = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();
    return newimage;
}

+ (UIImage*)imageWithImage:(UIImage *)image fitInsideWidth:(float)width fitInsideHeight:(float)height {
    if (image.size.height >= image.size.width) {
        return [MyImage imageWithImage:image convertToWidth:width];
    } else {
        return [MyImage imageWithImage:image convertToHeight:height];
    }
}

+ (UIImage*)imageWithImage:(UIImage *)image fitOutsideWidth:(float)width fitOutsideHeight:(float)height {
    if (image.size.height >= image.size.width) {
        return [MyImage imageWithImage:image convertToHeight:height];
    } else {
        return [MyImage imageWithImage:image convertToWidth:width];
    }
}

+ (UIImage*)imageWithImage:(UIImage *)image cropToWidth:(float)width cropToHeight:(float)height {
    CGSize size = [image size];
    CGRect rect = CGRectMake(((size.width-width) / 2.0f), ((size.height-height) / 2.0f), width, height);
    CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], rect);
    UIImage * img = [UIImage imageWithCGImage:imageRef]; 
    CGImageRelease(imageRef);
    return img;
}

@end

Answer 2

您必须以编程方式设置滚动视图的zoomScale：

yourImageView = [[UIImageView alloc] initWithImage:yourImage];
[yourScrollView addSubview:self.imageView];
yourScrollview.contentSize = yourImageView.bounds.size;

[yourScrollView setZoomScale:yourScrollView.bounds.size.width/yourImageView.bounds.size.width animated:NO];