访问任意 MacOS 应用程序的帧缓冲区

Question

我正在尝试为 Mac 上的任意应用程序捕获帧缓冲区并逐帧处理帧缓冲区。有没有办法利用应用程序内部帧缓冲区？我还注意到有一些 Graphics API 函数，例如 this 可以捕获整个屏幕，但我担心

A) 我需要弄清楚我的 window 在哪里并将其从整个屏幕图像中裁剪掉，这可能需要非零时间

B) 因为它捕获整个屏幕而不是一个 window，我想它会花费更长的时间。

我希望能够每秒捕捉和处理 20 帧，所以速度非常重要。

Answer 1

我有几个想法...

首先，也是最简单的，您可以启动 Quicktime（随 macOS 提供）并转到 File->New screen recording 并录制一个屏幕的任意区域并将其保存在电影中，稍后分析帧。

其次，您可以使用 screencapture (/usr/sbin/screencapture) 并指定要捕获的矩形或 window id。手册页不正确且垃圾，所以使用以下内容查看实际选项：

screencapture -h

输出

usage: screencapture [-icMPmwsWxSCUtoa] [files]
  -c         force screen capture to go to the clipboard
  -b         capture Touch Bar - non-interactive modes only
  -C         capture the cursor as well as the screen. only in non-interactive modes
  -d         display errors to the user graphically
  -i         capture screen interactively, by selection or window
               control key - causes screen shot to go to clipboard
               space key   - toggle between mouse selection and
                             window selection modes
               escape key  - cancels interactive screen shot
  -m         only capture the main monitor, undefined if -i is set
  -M         screen capture output will go to a new Mail message
  -o         in window capture mode, do not capture the shadow of the window
  -P         screen capture output will open in Preview
  -I         screen capture output will in a new Messages message
  -s         only allow mouse selection mode
  -S         in window capture mode, capture the screen not the window
  -t<format> image format to create, default is png (other options include pdf, jpg, tiff and other formats)
  -T<seconds> Take the picture after a delay of <seconds>, default is 5
  -w         only allow window selection mode
  -W         start interaction in window selection mode
  -x         do not play sounds
  -a         do not include windows attached to selected windows
  -r         do not add dpi meta data to image
  -l<windowid> capture this windowsid
  -R<x,y,w,h> capture screen rect
  -B<bundleid> screen capture output will open in app with bundleidBS
  files   where to save the screen capture, 1 file per screen

如您所见，-l、-R 选项非常有用。

我写了一个小程序来获取 windowids .

的列表

window 的大小和文件格式对速度有影响。我发现 JPEG 通常最快，而 PNG 通常最慢。我可以每秒以合理的大小 window 获得 20 帧：

time for i in {0..99}; do screencapture -l 56 -t jpg fred-$i.jpg; done

我在另一个链接的答案中从 windowlist 程序中得到 56。

访问任意 MacOS 应用程序的帧缓冲区

Access framebuffer for arbitrary MacOS application

macos

graphics

framebuffer

macos-sierra