ios小技巧总结：image相关

相册图片选择器
https://github.com/banchichen/TZImagePickerController

由URL获取图片（异步加载）

SDWebImage用法，只需要提供一个下载的url和占位图，就可以在回调里拿到下载后的图片

• imageview控件使用

#import 

[imageview sd_setImageWithURL:[NSURL URLWithString:@"......"] placeholderImage:[UIImage imageNamed:@"placeholder"] completed:^(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL) {

        imageview.image = image;
        NSLog(@"图片加载完成");
    }];

// 也可以图片下载完成后，直接显示下载后的图片
[imageview sd_setImageWithURL:[NSURL URLWithString:@"....."]];

• Button控件使用

#import 

[self.headBtn sd_setImageWithURL:[NSURL URLWithString:headImgUrl] forState:UIControlStateNormal placeholderImage:[UIImage imageNamed:@"登录2"]];

由URL获取图片（同步加载）

    NSString *imgurl = @".....";
    NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:imgurl]];
    UIImage *img3 = [UIImage imageWithData:data];

截屏

-(void)cutScreenPic{
    //开启上下文
    CGSize  imageSize = self.view.bounds.size;
    UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0.0);

    //将某个View的所有内容渲染到图形的上下文
    CGContextRef context = UIGraphicsGetCurrentContext();
    [self.view.layer renderInContext:context];
    //获得图片
    UIImage * image = UIGraphicsGetImageFromCurrentImageContext();
    //保存
    [UIImagePNGRepresentation(image) writeToFile:@"/Users/CC/Desktop/imageName.png" atomically:YES];
}

改变图片渲染方式（设置Rander）

    img = [img imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];  

压缩图片

/*  压缩图片至 指定像素  */
- (UIImage *)rescaleImageToPX:(CGFloat )toPX{
    CGSize size = self.size;
    
    if(size.width <= toPX && size.height <= toPX)
        return self;    //  图片如果比指定像素小，不需压缩
    
    CGFloat scale = size.width / size.height;   //比例
    
    if(size.width > size.height){
        size.width = toPX;
        size.height = size.width / scale;
    }
    else{
        size.height = toPX;
        size.width = size.height * scale;
    }
    
    return [self rescaleImageToSize:size];
}

/*  压缩图片至 指定尺寸   */
- (UIImage *)rescaleImageToSize:(CGSize)size
{
    CGRect rect = (CGRect){CGPointZero, size};
    
    UIGraphicsBeginImageContext(rect.size);
    
    [self drawInRect:rect];
    
    UIImage *resImage = UIGraphicsGetImageFromCurrentImageContext();
    
    UIGraphicsEndImageContext();
    
    return resImage;
}

保存图片到本地

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"Image.png"];

[UIImagePNGRepresentation(image) writeToFile:filePath atomically:YES];

多选图片

http://www.jianshu.com/p/6181f32bb844

聊天泡泡尖角图片

http://www.jianshu.com/p/c6c645394b06

比较两个图片是否相等

- (BOOL)image:(UIImage *)image1 isEqualTo:(UIImage *)image2
{
    NSData *data1 = UIImagePNGRepresentation(image1);
    NSData *data2 = UIImagePNGRepresentation(image2);

    return [data1 isEqual:data2];
}

设置图片圆角、圆形图片

//  封装工具方法
- (UIImage *)cutCircleImage {
    UIGraphicsBeginImageContextWithOptions(self.size, NO, 0.0);
    // 获取上下文
    CGContextRef ctr = UIGraphicsGetCurrentContext();
    // 设置圆形
    CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
    CGContextAddEllipseInRect(ctr, rect);
    // 裁剪
    CGContextClip(ctr);
    // 将图片画上去
    [self drawInRect:rect];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return image;
}

图片上传

用AFN3.0进行上传操作

//首先压缩图片
NSData *imageData = UIImageJPEGRepresentation(_imageV.image, 0.1);

- (void)upLoad{

    //1. 创建管理者对象
    AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
    //2. 地址、参数，用字典保存。不需要的可以省略。
    NSDictionary *dict = [[NSDictionary alloc] initWithObjectsAndKeys:_fireID,@"id",_longitude,@"longitude",_latitude,@"latitude", nil];
  
    NSString *urlString = @“... ...”；//（后台给你url）

    //3. post请求
    [manager POST:urlString parameters:dict constructingBodyWithBlock:^(id  _Nonnull formData) {

    // 在网络开发中，上传文件时不允许文件重名，解决方案：
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
     formatter.dateFormat   = @"yyyyMMddHHmmss";    // 设置时间格式
     NSString *str   = [formatter stringFromDate:[NSDate date]];

     NSString *fileName  = [NSString stringWithFormat:@"%@.png", str];

         /*
         此方法参数：
             1. 要上传的[二进制数据]
             2. imgFile是对应后台给你url里面的图片参数。
             3. 要保存在服务器上的[文件名]
             4. 上传文件的[mimeType]
        */     
     [formData appendPartWithFileData:imageData name:@"imgFile" fileName:fileName mimeType:@"image/png"];

    } progress:^(NSProgress * _Nonnull uploadProgress) {
        // 上传进度
        NSLog(@"%lf",1.0 *uploadProgress.completedUnitCount / uploadProgress.totalUnitCount);     

    } success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {

        NSLog(@"请求成功：%@",responseObject);

    } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {

        NSLog(@"请求失败：%@",error);
    }];
}

判断图片类型

//封装工具方法。通过图片Data数据第一个字节 来获取图片扩展名
- (NSString *)contentTypeForImageData:(NSData *)data {
    uint8_t c;
    [data getBytes:&c length:1];
    switch (c) {
        case 0xFF:
            return @"jpeg";
        case 0x89:
            return @"png";     
        case 0x47:
            return @"gif";        
        case 0x49:   
        case 0x4D:
            return @"tiff";        
        case 0x52:  
            if ([data length] < 12) {
                return nil;
            }
            NSString *testString = [[NSString alloc] initWithData:[data subdataWithRange:NSMakeRange(0, 12)] encoding:NSASCIIStringEncoding];
            if ([testString hasPrefix:@"RIFF"] && [testString hasSuffix:@"WEBP"])        
            {
                return @"webp";
            }
            return nil;
    }
    return nil;
}

//外界调用
//假设这是一个网络获取的URL
    NSString *path = @"http://pic.rpgsky.net/images/2016/07/26/3508cde5f0d29243c7d2ecbd6b9a30f1.png";
    NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:path]];
    //调用获取图片扩展名
    NSString *string = [self contentTypeForImageData:data];
    //输出结果为 png
    NSLog(@"%@",string);

在图片上绘制文字

//自定义工具方法
- (UIImage *)imageWithTitle:(NSString *)title fontSize:(CGFloat)fontSize
{
        //画布大小
        CGSize size=CGSizeMake(self.size.width,self.size.height);
        //创建一个基于位图的上下文
        UIGraphicsBeginImageContextWithOptions(size,NO,0.0);//opaque:NO  scale:0.0
        [self drawAtPoint:CGPointMake(0.0,0.0)];
        //文字居中显示在画布上
        NSMutableParagraphStyle* paragraphStyle = [[NSParagraphStyle       defaultParagraphStyle] mutableCopy];
        paragraphStyle.lineBreakMode = NSLineBreakByCharWrapping;
        paragraphStyle.alignment=NSTextAlignmentCenter;//文字居中
        //计算文字所占的size,文字居中显示在画布上
        CGSize sizeText=[title boundingRectWithSize:self.size options:NSStringDrawingUsesLineFragmentOrigin
attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:fontSize]}context:nil].size;
        CGFloat width = self.size.width;
        CGFloat height = self.size.height;
        CGRect rect = CGRectMake((width-sizeText.width)/2, (height-sizeText.height)/2, sizeText.width, sizeText.height);
        //绘制文字
        [title drawInRect:rect withAttributes:@{ NSFontAttributeName:[UIFont systemFontOfSize:fontSize],NSForegroundColorAttributeName:[ UIColor whiteColor],NSParagraphStyleAttributeName:paragraphStyle}];
        //返回绘制的新图形
        UIImage *newImage= UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        return newImage;
}

拉伸图片

例子：QQ会话窗口，气泡的背景图片拉伸

//   自定义工具方法
+ (UIImage *)resizeWithImage:(UIImage *)image{
    CGFloat top = image.size.height/2.0;
    CGFloat left = image.size.width/2.0;
    CGFloat bottom = image.size.height/2.0;
    CGFloat right = image.size.width/2.0;
    return [image resizableImageWithCapInsets:UIEdgeInsetsMake(top, left, bottom, right)resizingMode:UIImageResizingModeStretch];
}

- (UIImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets resizingMode:(UIImageResizingMode)resizingMode；
//此方法返回返回拉伸后的图像。第二个参数resizingMode是图像拉伸模式:
UIImageResizingModeTile 平铺 、UIImageResizingModeStretch,  拉伸

获得灰度图

+ (UIImage*)covertToGrayImageFromImage:(UIImage*)sourceImage
{
    int width = sourceImage.size.width;
    int height = sourceImage.size.height;

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
    CGContextRef context = CGBitmapContextCreate (nil,width,height,8,0,colorSpace,kCGImageAlphaNone);
    CGColorSpaceRelease(colorSpace);

    if (context == NULL) {
        return nil;
    }

    CGContextDrawImage(context,CGRectMake(0, 0, width, height), sourceImage.CGImage);
    CGImageRef contextRef = CGBitmapContextCreateImage(context);
    UIImage *grayImage = [UIImage imageWithCGImage:contextRef];
    CGContextRelease(context);
    CGImageRelease(contextRef);

    return grayImage;
}

由View生成图片

- (UIImage *)makeImageWithView:(UIView *)view withSize:(CGSize)size
{
// 下面方法：第一个参数 表示区域大小。
第二个参数 表示是否非透明。半透明效果需要传NO，否则传YES。
第三个参数 是屏幕密度 [UIScreen mainScreen].scale。
    UIGraphicsBeginImageContextWithOptions(size, NO, [UIScreen mainScreen].scale);
    [view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

生成纯色图片

- (UIImage *)imageWithColor:(UIColor *)color {
    // 描述矩形
    CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);
    // 开启位图上下文
    UIGraphicsBeginImageContext(rect.size);
    // 获取位图上下文
    CGContextRef context = UIGraphicsGetCurrentContext();
    // 使用color演示填充上下文
    CGContextSetFillColorWithColor(context, [color CGColor]);
    // 渲染上下文
    CGContextFillRect(context, rect);
    // 从上下文中获取图片
    UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();
    // 结束上下文
    UIGraphicsEndImageContext();
   
     return theImage;
}

毛玻璃效果

QQ.png

根据bundle中的文件名读取图片

+ (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;
}

保存图片到本地相册

-(void)saveImage:(UIImage *)img{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        
        UIImageWriteToSavedPhotosAlbum(img, self, @selector(image:didFinishSavingWithError:contextInfo:), NULL);
        
    });
}

- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo{
        
    if(error != NULL){
        [SVProgressHUD showNOmessage:@"保存失败"];
    }else{
        [SVProgressHUD showYESmessage:@"保存成功"];
    }
    
}

图片合并

//图片合成
+ (UIImage *)imageCombineImage:(UIImage *)useImage maskImage:(UIImage *)maskImage
{
    UIGraphicsBeginImageContextWithOptions(useImage.size ,NO, 0.0);
    
    [useImage drawInRect:CGRectMake(0, 0, useImage.size.width, useImage.size.height)];
    
    //四个参数为水印图片的位置
    [maskImage drawInRect:CGRectMake(50, 50, 50, 50)];

    //如果要多个位置显示，继续drawInRect就行
    //[maskImage drawInRect:CGRectMake(0, useImage.size.height/2, useImage.size.width, useImage.size.height/2)];
    UIImage *resultImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return resultImage;
}

UIImage和Base64格式图片相互转化

/* 方法一 */
- (NSString *)encodeToBase64String:(UIImage *)image {
 return [UIImagePNGRepresentation(image) base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];
}

- (UIImage *)decodeBase64ToImage:(NSString *)strEncodeData {
  NSData *data = [[NSData alloc]initWithBase64EncodedString:strEncodeData options:NSDataBase64DecodingIgnoreUnknownCharacters];
  return [UIImage imageWithData:data];
}


/* 方法二 */
- (BOOL) imageHasAlpha: (UIImage *) image  {  
    CGImageAlphaInfo alpha = CGImageGetAlphaInfo(image.CGImage);  
    return (alpha == kCGImageAlphaFirst ||  
            alpha == kCGImageAlphaLast ||  
            alpha == kCGImageAlphaPremultipliedFirst ||  
            alpha == kCGImageAlphaPremultipliedLast);  
}  

- (NSString *) image2DataURL: (UIImage *) image  {  
    NSData *imageData = nil;  
    NSString *mimeType = nil;  
  
    if ([self imageHasAlpha: image]) {  
        imageData = UIImagePNGRepresentation(image);  
        mimeType = @"image/png";  
    } else {  
        imageData = UIImageJPEGRepresentation(image, 1.0f);  
        mimeType = @"image/jpeg";  
    }  
  
    return [NSString stringWithFormat:@"data:%@;base64,%@", mimeType,  
           [imageData base64EncodedStringWithOptions: 0]];  
}  
- (UIImage *) dataURL2Image: (NSString *) imgSrc  
{  
    NSURL *url = [NSURL URLWithString: imgSrc];  
    NSData *data = [NSData dataWithContentsOfURL: url];  
    UIImage *image = [UIImage imageWithData: data];  
  
    return image;  
}  

图片处理

https://github.com/lisongrc/UIImage-Categories