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

- (void)viewDidLoad {[super viewDidLoad];//注册用户的截屏操作通知
    [[NSNotificationCenter defaultCenter] addObserver:selfselector:@selector(userDidTakeScreenshot:)name:UIApplicationUserDidTakeScreenshotNotification object:nil];
}

// 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];
}

/***  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;elseimageSize = 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;
}

- (void)viewWillDisappear:(BOOL)animated {[super viewWillDisappear:animated];[[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationUserDidTakeScreenshotNotification object:nil];}

// 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;
}

// 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;
}

// 图片压缩
+ (UIImage *)compressImage:(UIImage *)image toByte:(NSUInteger)maxLength {// Compress by qualityCGFloat compression = 0.7;//UIImage转换为NSDataNSData *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 sizeNSUInteger 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;
}