116 lines
4.3 KiB
PowerShell
116 lines
4.3 KiB
PowerShell
<#
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.SYNOPSIS
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Extracts a specific frame or the last frame of a video file to a PNG image using ffmpeg.
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.PARAMETER Video
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Path to the input video file. Can be absolute or relative to current directory.
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.PARAMETER Image
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Path to the output PNG image file. Can be absolute or relative to current directory.
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Supports a printf-style numbering token (e.g. frame_%04d.png or C:\Output\frame_%04d.png), which is
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replaced with the extracted 0-based frame index, zero-padded to the width given in the token
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(%d = no padding, %04d = 4 digits). Without a token the path is used literally.
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The output directory is created when it does not exist.
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.PARAMETER Frame
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0-based frame index to extract. Negative values count from the end:
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-1 extracts the last frame (default), -2 extracts second-to-last, etc.
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The resulting frame index is clamped to the valid range (0 to total frames - 1): a positive value past the last frame
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gives the last frame, and a negative value before the first frame gives frame 0.
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.DESCRIPTION
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Extracts a specific frame of a video file to a PNG image using ffmpeg.
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Supports negative frame indices to count from the end of the video.
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Supports a printf-style numbering token in -Image, like Get-FramesRange.ps1.
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Supports -WhatIf and -Confirm for safe execution.
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#>
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[CmdletBinding(SupportsShouldProcess)]
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param(
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[Parameter(Mandatory = $true)]
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[string]$Video,
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[Parameter(Mandatory = $true)]
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[string]$Image,
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[Parameter(Mandatory = $false)]
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[int]$Frame = -1
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)
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Set-StrictMode -Version Latest
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$ErrorActionPreference = 'Stop'
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$VideoPath = $Video
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if (-not (Test-Path -LiteralPath $VideoPath)) {
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Write-Error ('Video file not found: {0}' -f $VideoPath)
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exit 1
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}
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$PSNativeCommandUseErrorActionPreference = $false
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$totalFrames = & ffprobe -v error -select_streams v:0 -count_frames -show_entries stream=nb_read_frames -of csv=p=0 -- $VideoPath 2>&1 | Select-Object -First 1
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if (-not $totalFrames -or $totalFrames -notmatch '^\d+$') {
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Write-Error ('Could not determine frame count for: {0}' -f $VideoPath)
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exit 1
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}
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$totalFramesInt = [int]$totalFrames
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if ($totalFramesInt -lt 1) {
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Write-Error ('Video has no frames: {0}' -f $VideoPath)
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exit 1
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}
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$maxFrameIndex = $totalFramesInt - 1
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# Negative values count from the end; the result is clamped to [0, maxFrameIndex]
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$requestedFrame = if ($Frame -lt 0) { $totalFramesInt + $Frame } else { $Frame }
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$frameToExtract = [Math]::Max(0, [Math]::Min($requestedFrame, $maxFrameIndex))
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Write-Host ('Total frames: {0} - extracting frame index {1}' -f $totalFramesInt, $frameToExtract)
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# Resolve any printf-style numbering token (%d, %04d) in -Image to the extracted frame
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# index. The substitution is done here rather than left to ffmpeg: ffmpeg would treat the
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# token as an image2 sequence counter starting at 1 instead of the actual video frame index.
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$ImagePath = $Image
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$tokenPattern = [regex]'%(\d*)d'
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while ($ImagePath -match $tokenPattern) {
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$padWidth = if ($Matches[1]) { [int]$Matches[1] } else { 0 }
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$ImagePath = $tokenPattern.Replace($ImagePath, ([string]$frameToExtract).PadLeft($padWidth, '0'), 1)
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}
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if ($ImagePath -ne $Image) {
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Write-Host ('Output pattern resolved to: {0}' -f $ImagePath)
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}
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$outputDir = Split-Path -Parent $ImagePath
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if ($outputDir -and -not (Test-Path -LiteralPath $outputDir)) {
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if ($PSCmdlet.ShouldProcess($outputDir, 'Create output directory')) {
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New-Item -ItemType Directory -Path $outputDir -Force | Out-Null
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Write-Host ('Created output directory: {0}' -f $outputDir)
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}
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}
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if ($PSCmdlet.ShouldProcess($ImagePath, ('Extract frame {0} to PNG' -f $frameToExtract))) {
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$videoFilter = 'select=eq(n\,{0})' -f $frameToExtract
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$ffmpegArgs = @(
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'-y'
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'-i', $VideoPath
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'-vf', $videoFilter
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'-fps_mode', 'vfr'
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'-frames:v', '1'
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'-q:v', '1'
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'--', $ImagePath
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)
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$ffmpegStderr = & ffmpeg @ffmpegArgs 2>&1
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if ($LASTEXITCODE -ne 0) {
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Write-Error ('ffmpeg failed to extract frame {0}: {1}' -f $frameToExtract, (($ffmpegStderr | Out-String).Trim()))
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exit 1
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}
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if (-not (Test-Path -LiteralPath $ImagePath)) {
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Write-Error ('ffmpeg reported success but no image was written for frame {0}: {1}' -f $frameToExtract, $ImagePath)
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exit 1
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}
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Write-Host ('Frame saved to: {0}' -f $ImagePath)
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}
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