本文共 8997 字，大约阅读时间需要 29 分钟。
1.UIImageView中的视图内容显示模式
UIImageView *imageV=[[UIImageViewalloc]init];
imageV.scaleToFill------默认缩放填充;
imageV.scaleAspectfit-------有留白;
imageV.AspectFill------自适应填充,视图会被裁剪;
2.UIImageView显示圆形图片
设置圆形图像的原理很简单，通过设置UIImageView的圆角属性即可。首先我们需要保证待设置的图片资源大小为方形的（稍后我们会提供图像裁剪方法）。方法一
//设置图像显示控件为圆形 - (void)changeToCirclePicture { //设置圆角半径为方形边长一半 [self.imageView.layer setCornerRadius:CGRectGetHeight([self.imageView bounds]) / 2]; [self.imageView.layer setMasksToBounds:YES]; //设置边框宽度和颜色 [self.imageView.layer setBorderWidth:10]; [self.imageView.layer setBorderColor:[[UIColor grayColor] CGColor]]; } +++++++++++
方法一
UIImageView *imageView1 = [[UIImageViewalloc] initWithImage:[UIImageimageNamed:@"11.png"]];
imageView1.frame = CGRectMake(60,100, 100, 100);
imageView1.layer.masksToBounds =YES;
imageView1.layer.cornerRadius =50;
[self.view addSubview:imageView1];
++++++++++++++++++++++++
方法二:
UIImageView *imageView2 = [[UIImageViewalloc] initWithFrame:CGRectMake(60,250, 100,100)];
UIImage *image2 = [UIImageimageNamed:@"12.png"];
imageView2.image = [self circleImage:image2 withParam:0];//调用下面的方法
[self.view addSubview:imageView2];
-(UIImage*) circleImage:(UIImage*) image withParam:(CGFloat) inset {
UIGraphicsBeginImageContext(image.size);
CGContextRef context =UIGraphicsGetCurrentContext();
//圆的边框宽度为2，颜色为红色
CGContextSetLineWidth(context,2);
CGContextSetStrokeColorWithColor(context, [UIColorredColor].CGColor);
CGRect rect = CGRectMake(inset, inset, image.size.width - inset *2.0f, image.size.height - inset *2.0f);
CGContextAddEllipseInRect(context, rect);
CGContextClip(context);
//在圆区域内画出image原图
[image drawInRect:rect];
CGContextAddEllipseInRect(context, rect);
CGContextStrokePath(context);
//生成新的image
UIImage *newimg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newimg;
}
虽然我们这个demon中并没有用到图片的裁剪，但是很有可能实践项目中会涉及到图片裁剪成正方形。裁剪算法也很简单，以最短边边长为裁剪正方形的边长，在图像剧中的位置进行裁剪。
//截取居中的方形图像 - (UIImage *)cutPicture:(UIImage *)raw { CGSize origImageSize = raw.size; CGRect newRect = CGRectMake(0, 0, SCREEN_WIDTH, SCREEN_WIDTH); float ratio = MAX(newRect.size.width / origImageSize.width, newRect.size.height / origImageSize.height); //开启透明位图上下文 UIGraphicsBeginImageContextWithOptions(newRect.size, NO, 0.0); //创建圆角矩形的对象，这里设置圆角为0 UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:newRect cornerRadius:0.0]; //裁剪图形上下文 [path addClip]; //让图片在缩略图绘制范围内居中 CGRect projectRect; projectRect.size.width = ratio * origImageSize.width; projectRect.size.height = ratio * origImageSize.height; projectRect.origin.x = (newRect.size.width - projectRect.size.width) / 2.0; projectRect.origin.y = (newRect.size.height - projectRect.size.height) / 2.0; //在上下文中绘制图片 [raw drawInRect:projectRect]; //从上下文获取图片，并复制给item UIImage *smallImage = UIGraphicsGetImageFromCurrentImageContext(); //清理图形上下文 UIGraphicsEndImageContext(); return smallImage; }
=+++++++++++++++++++++++++++++++++++++++++++++++
UIIMage
1.创建UIIMage
UIImage *image=[UIImage imageWithData:data];
UIImage *image2=[UIImage imageWithData:data scale:0.5];
UIImage *img=[UIIMage imageWithCGImage:<#(nonnull CGImageRef)#>];//加载的时候,1个像素就是一个点;
UIImage *img=[UIImage imageWithCGImage:<#(nonnull CGImageRef)#> scale:<#(CGFloat)#> orientation:<#(UIImageOrientation)#>];//可以设置缩放比例
UIImage *img=[UIImage imageNamed:<#(nonnull NSString *)#>];//图片会常驻内存中,直接从内存读取
UIImage *img=[UIImage imageWithContentsOfFile:<#(nonnull NSString *)#>];//不做缓存,从bundle路径中加载.速度慢
UIImage *image=[btn bacgaroundImageForState:UIViewControllerShowDetailTargetDidChangeNotification];//btn是按钮,从按钮中获取图片
//将图片转换成二进制
NSData *data= UIImagePNGRepresentation(img);
2.图片拉伸
UIImage *resizeImage=[img resizableImageWithCapsets:UIEdgeInsetsMake(self.view.bounds.size.width/2,self.view.bounds.size.width/2,self.view.bounds.size.width/2,self.view.bounds.size.width/2) resizingmode:UIImageResizingModeStretch];//UIImageResizingModeTitle是平铺,iOS5.0后
UIImage *image=[img stretchableImageWithleftcapWidth:self.view.bounds.size.width*0.5 topcapheight:self.view.bounds.size.height*0.5]; //iOS5.0 前
++++++++++++绘图封装一个背景图片
//首先封装了一个方法,用来生成背景图片
- (UIImage *) imageWithFrame:(CGRect)frame alphe:(CGFloat)alphe {
frame = CGRectMake(0, 0, frame.size.width, frame.size.height);
UIColor *redColor = [UIColorcolorWithRed:0green:0blue:0alpha:alphe];
UIGraphicsBeginImageContext(frame.size);
CGContextRef context =UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context, [redColorCGColor]);
CGContextFillRect(context, frame);
UIImage *theImage =UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return theImage;
}
===========
直接用图片设置View的背景，会因版本和手机大小产生变形，解决办法，创建一个UIIMageview 加到View上；
========计算图片占内存的大小；NSData * imageData = UIImageJPEGRepresentation(image,1);
length = [imageData length]/1000；//获得是MB
==============
SDWEIMage回调中获取宽高；
UIImageView *imageView = [[UIImageView alloc]init];[imageView sd_setImageWithURL:[NSURL URLWithString:@"http://"] placeholderImage:niloptions:SDWebImageRetryFailed completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) { NSLog(@"宽：%f, 高：%f", image.size.width, image.size.height);}]; 先引入系统的ImageIO.framework库
CGSize size = [UIImage getImageSizeWithURL:@"http://"];NSLog(@"宽：%f, 高：%f", size.width, size.height);
计算图片的size：
UIImage *image=[UIImage imageWithData:data];
图片的尺寸：image.size
===============图片的下载：
方法一：imageUrl是图片的下载地址
NSData *data=[NSData dataWithContentsOfURL:[NSURL URLWithString:imageUrl]];
// UIImage *image=[UIImage imageWithData:data];
// [self.imageIMArr addObject:image];
方法二：
#import <SDWebImageDownloader.h>
SDWebImageDownloader *downloader = [SDWebImageDownloadersharedDownloader];
[downloader downloadImageWithURL:[NSURLURLWithString:imageUrl]
options:0
progress:^(NSInteger receivedSize,NSInteger expectedSize) {
}
completed:^(UIImage *image,NSData *data,NSError *error,BOOL finished) {
if (image && finished) {
//缩小图片
CGSize newSize=CGSizeMake(118,118);
UIGraphicsBeginImageContext(newSize);
[image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
image= [UIGraphicsGetImageFromCurrentImageContext()imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];//从图形上下文获取新的图片
UIGraphicsEndImageContext();
[self.imageIMArraddObject:image];
if(self.imageIMArr.count==self.dataArr.count){
[self.tabreloadData];
NSLog(@"sdwebxiazai ");
[weakSelf.tab.headerendRefreshing];
}
}
}];
===========UIIMageView分类：
#import <UIKit/UIKit.h>
@interface UIImageView (LYImageview)
+(UIImageView *)initImageviewWithDict:(NSDictionary *)dict;
@end
#import "UIImageView+LYImageview.h"
@implementation UIImageView (LYImageview)
+(UIImageView *)initImageviewWithDict:(NSDictionary *)dict{
UIImageView *imageV=[[UIImageViewalloc]init];
imageV.image=[UIImageimageNamed:dict[@"image"]];
imageV.contentMode=
UIViewContentModeScaleToFill;//图片显示模式
// UIViewContentModeScaleToFill, 使图片缩放来填充满imageView.
// UIViewContentModeScaleAspectFit, 使图片保持原比例, 并且全部显示在imgeView上, 但是可能导致空白区域.
// UIViewContentModeScaleAspectFill, 使图片保持原比例, 并且填充满整个imageView, 但可能会导致只显示部分图片.
return imageV;
}
@end
调用：
NSDictionary *imageDict=@{
@"image":@"left"
};
UIImageView *imageV=[UIImageViewinitImageviewWithDict:imageDict];
imageV.frame=CGRectMake(50,150, 100, 100);
[self.viewaddSubview:imageV];
============================UIImage imagewithcontentfile:
+ (UIImage *)imageWithFileName:(NSString *)name { NSString *extension = @"png"; NSArray *components = [name componentsSeparatedByString:@"."]; if ([components count] >= 2) { NSUInteger lastIndex = components.count - 1; extension = [components objectAtIndex:lastIndex]; name = [name substringToIndex:(name.length-(extension.length+1))]; } // 如果为Retina屏幕且存在对应图片，则返回Retina图片，否则查找普通图片 if ([UIScreen mainScreen].scale == 2.0) { name = [name stringByAppendingString:@"@2x"]; NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:extension]; if (path != nil) { return [UIImage imageWithContentsOfFile:path]; } } if ([UIScreen mainScreen].scale == 3.0) { name = [name stringByAppendingString:@"@3x"]; NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:extension]; if (path != nil) { return [UIImage imageWithContentsOfFile:path]; } } NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:extension]; if (path) { return [UIImage imageWithContentsOfFile:path]; } return nil;} +(UIImage *)imageNamedss:(NSString *)name{ //高效 NSString *resourcePath = [[NSBundle mainBundle] resourcePath]; NSString *filePath = [resourcePath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png",name]]; UIImage *image = [UIImage imageWithContentsOfFile:filePath]; return image;}
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