Why Does Piping Raw Image Bytes Through a PowerShell Function Fail?
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MellowPine47
Why does piping ImageMagick's raw PNG output directly into chafa work, while wrapping chafa in a PowerShell function causes it to fail? The direct command works in PowerShell 7.6: `magick _.png -negate png:- | chafa --size=70x -f sixel -`. However, this function-based version does not: `function img { chafa.exe --size=70x -f sixel @args }` followed by `magick _.png -negate png:- | img -`. The goal is to preserve the raw byte stream and have chafa read it from standard input.
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PowerShell can pass native stdout as raw bytes when one native executable is directly piped to another. In the second command, the pipeline target is a PowerShell function, so PowerShell handles the data through its object pipeline instead of connecting the native programs' standard streams directly. The bytes are no longer preserved as a raw stdin stream for chafa.
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The function also doesn't receive or forward pipeline input. `img -` doesn't automatically mean “read stdin” here; the dash is just an argument, and PowerShell functions don't interpret it like a native program does. You would need a pipeline-bound parameter and code that explicitly writes the received data to the child process's standard input using .NET APIs such as `System.Diagnostics.Process`.
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The direct form works because chafa itself understands `-` and has the native-program logic needed to read standard input. Your wrapper currently just launches `chafa.exe --size=70x -f sixel` and ignores anything arriving at the function. For this raw-byte case, the simplest solution is to keep the native commands directly connected rather than putting a PowerShell function between them.
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