Powershell: replacing pixel-values found in text file with their equivalent em-entries, taking the data from a csv-File

Question

So, I have got another question here, kind of following up my first one. Scenario: I have a text file (it’s actually a scss file) that has got a lot of different entries for pixels, Like f.e. margin-width: 14px; padding: 10px 20px; .. etc. I also made a csv-file containing a lot of entries, first column: value in pixels, second column: value in ems. No I want to exchange every pixel-value found in my file with the equivalent em-value. Can anybody help me with that?

Ok, thanks for the fast reply here is some more info: This is a part of my scss-file (the textfile)

#anmelden+#NewsletterAbmeldung {
background-color: #efefef;
padding: 23px 23px 20px;
border-radius: 7px;
border: 1px solid #d9d9d9;
}

And here a few lines from csv-file

..
7px;0,44em
..
20px;1,25em
21px;1,31em
22px;1,38em
23px;1,44em

It holds pixel-sizes and their equivalents in ems. So what I would like the script to do is that whenever the first (px) entry is found, I should be replaced by the second (em)-entry. My code in the end would look like this:

#anmelden+#NewsletterAbmeldung {
background-color: #efefef;
padding: 1,44em 1,44em 1,25em;
border-radius: 0,44em;
border: 0,06em solid #d9d9d9;
}

Answer 1

Using your conversion csv file, you could do this:

$content = (Get-Content -Path 'D:\Test\YourSCSS.txt' -Raw)
Import-Csv -Path 'D:\Test\emConversion.csv' -Delimiter ';' -Header Pixel, Em | ForEach-Object {
    $content = $content -replace $_.Pixel, $_.Em
}

# save as (new) file
$content | Set-Content -Path 'D:\Test\YourSCSS_em.txt'

However, looking at the converted values, it is clear you used the standard calculation, where the default font size is 16px and therefore 1px equals 0.0625em.

Knowing this, you don't need the csv at all and can do the math straight away like this:

$content = (Get-Content -Path 'D:\Test\YourSCSS.txt' -Raw)
$match = [regex]::Match($content, '((\d+)px)')
while ($match.Success) {
    $emValue = '{0:F2}em' -f (0.0625 * [double]$match.Groups[2].Value)
    $content = $content -replace $match.Groups[1].Value, $emValue
    $match   = $match.NextMatch()
}

# save as (new) file
$content | Set-Content -Path 'D:\Test\YourSCSS_em.txt'

Using the second code also eliminates the need for creating a file with all possible pixel values and their equivalent em values (with the possibility of omitting some..)

---

If you're current culture formats numbers with a decimal comma, (same as my Dutch machine), you can replace line

$emValue = '{0:N2}em' -f (0.0625 * [double]$match.Groups[2].Value)

with

$emValue = "$([math]::Round(0.0625 * [double]$match.Groups[2].Value, 2))"
# or
# $emValue = (0.0625 * [double]$match.Groups[2].Value).ToString('F2',[CultureInfo]::InvariantCulture)

to get these values with a decimal point as should be used in CSS