iOS 关于监听手机截图,UIView生成UIImage, UIImage裁剪与压缩的总结

一.  关于监听手机截图

1. 背景: 发现商品的售价页总是被人转发截图,为了方便用户添加截图分享的小功能

首先要注册用户截屏操作的通知

- (void)viewdidload {
    [super viewdidload];
    //注册用户的截屏操作通知
    [[nsnotificationcenter defaultcenter] addobserver:self
                                             selector:@selector(userdidtakescreenshot:)
                                                 name:uiapplicationuserdidtakescreenshotnotification object:nil];
}

之后人为截图

// 截屏响应
- (void)userdidtakescreenshot:(nsnotification *)notification
{
    //人为截屏, 模拟用户截屏行为, 获取所截图片
    _screenshotimg = [uiutils imagewithscreenshot]; // 这里封装了一下 获得图片就可以取分享啦
    dhshareactionsheetscreenshot *sharealert = [[dhshareactionsheetscreenshot alloc] init];
    [sharealert showwithimg:_screenshotimg];
}

人为截图,在这里可以对图片进行一些操作,比如添加自己的app二维码啥的类似微博

/**
 *  截取当前屏幕 并修改
 */
+ (uiimage *)imagewithscreenshot
{
    cgsize imagesize = cgsizezero;
    uiinterfaceorientation orientation = [uiapplication sharedapplication].statusbarorientation;
    if (uiinterfaceorientationisportrait(orientation))
        imagesize = [uiscreen mainscreen].bounds.size;
    else
        imagesize = cgsizemake([uiscreen mainscreen].bounds.size.height, [uiscreen mainscreen].bounds.size.width);
    
    uigraphicsbeginimagecontextwithoptions(imagesize, no, 0);
    cgcontextref context = uigraphicsgetcurrentcontext();
    for (uiwindow *window in [[uiapplication sharedapplication] windows])
    {
        cgcontextsavegstate(context);
        cgcontexttranslatectm(context, window.center.x, window.center.y);
        cgcontextconcatctm(context, window.transform);
        cgcontexttranslatectm(context, -window.bounds.size.width * window.layer.anchorpoint.x, -window.bounds.size.height * window.layer.anchorpoint.y);
        if (orientation == uiinterfaceorientationlandscapeleft)
        {
            cgcontextrotatectm(context, m_pi_2);
            cgcontexttranslatectm(context, 0, -imagesize.width);
        }else if (orientation == uiinterfaceorientationlandscaperight)
        {
            cgcontextrotatectm(context, -m_pi_2);
            cgcontexttranslatectm(context, -imagesize.height, 0);
        } else if (orientation == uiinterfaceorientationportraitupsidedown) {
            cgcontextrotatectm(context, m_pi);
            cgcontexttranslatectm(context, -imagesize.width, -imagesize.height);
        }
        if ([window respondstoselector:@selector(drawviewhierarchyinrect:afterscreenupdates:)])
        {
            [window drawviewhierarchyinrect:window.bounds afterscreenupdates:yes];
        }
        else
        {
            [window.layer renderincontext:context];
        }
        cgcontextrestoregstate(context);
    }
    
    uiimage *image = uigraphicsgetimagefromcurrentimagecontext();
    uigraphicsendimagecontext();
    
    return  image;
}

当然最后不要忘记注销通知,这里要注意,根据需求来,如果商品详情页又可以跳转到别的商品详情页最好这样注销,

避免跳到别的商品详情页多次截图

- (void)viewwilldisappear:(bool)animated {
    [super viewwilldisappear:animated];
    [[nsnotificationcenter defaultcenter] removeobserver:self name:uiapplicationuserdidtakescreenshotnotification object:nil];

}

二. uiview生成uiimag

uiview生成uiimage 时可以转一下jpg格式,这样图片不会太大具体参数可以百度,屏幕密度我一般采用0.7;

// uiview生成图片
+(uiimage*)convertviewtoimage:(uiview*)v{
    cgsize s = v.bounds.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是非透明的。如果需要显示半透明效果，需要传no，否则传yes。第三个参数就是屏幕密度了
    //    nslog(@"[uiscreen mainscreen].scale-%f",[uiscreen mainscreen].scale);
    // 3.0 高清图 分享不了 用2.0即可 或者分享的时候压缩图片
    uigraphicsbeginimagecontextwithoptions(s, yes, [uiscreen mainscreen].scale);
    [v.layer renderincontext:uigraphicsgetcurrentcontext()];
    uiimage*image = uigraphicsgetimagefromcurrentimagecontext();
    uigraphicsendimagecontext();
    
    nsdata * data = uiimagejpegrepresentation(image, 0.7);
    uiimage* imagelast = [uiimage imagewithdata:data];
    
    return imagelast;
}

三. uiimage的裁剪

// 图片裁剪
+ (uiimage *)ct_imagefromimage:(uiimage *)image inrect:(cgrect)rect{
    
    //把像 素rect 转化为 点rect（如无转化则按原图像素取部分图片）
    cgfloat scale = [uiscreen mainscreen].scale;
    cgfloat x= rect.origin.x*scale,y=rect.origin.y*scale,w=rect.size.width*scale,h=rect.size.height*scale;
    cgrect dianrect = cgrectmake(x, y, w, h);
    
    //截取部分图片并生成新图片
    cgimageref sourceimageref = [image cgimage];
    cgimageref newimageref = cgimagecreatewithimageinrect(sourceimageref, dianrect);
    uiimage *newimage = [uiimage imagewithcgimage:newimageref scale:[uiscreen mainscreen].scale orientation:uiimageorientationup];
    
    nsdata * data = uiimagejpegrepresentation(newimage, 0.7);
    uiimage* imagelast = [uiimage imagewithdata:data];
    return imagelast;
}

四. uiimage的压缩

分享图片时根据分享的应用不同对图片大小是有限制的,微信是10m,但是qq小一些,

另外小程序分享的话也是有限制的128kb,当截图裁剪后无法满足时就需要压缩一下

先是密度压缩然后大小压缩,一般都可以解决的

// 图片压缩
+ (uiimage *)compressimage:(uiimage *)image tobyte:(nsuinteger)maxlength {
    // compress by quality
    cgfloat compression = 0.7;
    //uiimage转换为nsdata
    nsdata *data = uiimagejpegrepresentation(image, compression);
    if (data.length < maxlength){
        return image;
    }
    cgfloat max = 1;
    cgfloat min = 0;
    for (int i = 0; i < 6; ++i) {
        compression = (max + min) / 2;
        data = uiimagejpegrepresentation(image, compression);
        if (data.length < maxlength * 0.9) {
            min = compression;
        } else if (data.length > maxlength) {
            max = compression;
        } else {
            break;
        }
    }
    uiimage *resultimage = [uiimage imagewithdata:data];
    if (data.length < maxlength){
        return resultimage;
    }
    // compress by size
    nsuinteger lastdatalength = 0;
    while (data.length > maxlength && data.length != lastdatalength) {
        lastdatalength = data.length;
        cgfloat ratio = (cgfloat)maxlength / data.length;
        cgsize size = cgsizemake((nsuinteger)(resultimage.size.width * sqrtf(ratio)),
                                 (nsuinteger)(resultimage.size.height * sqrtf(ratio))); // use nsuinteger to prevent white blank
        uigraphicsbeginimagecontext(size);
        [resultimage drawinrect:cgrectmake(0, 0, size.width, size.height)];
        resultimage = uigraphicsgetimagefromcurrentimagecontext();
        uigraphicsendimagecontext();
        data = uiimagejpegrepresentation(resultimage, compression);
    }
    return resultimage;
}

这些是最近app的截图分享,小程序分享的关于图片的总结.希望帮助到需要的人.