In a previous tip we illustrated how you can convert any picture into a Base64-encoded string. Today, we'd like to show how you can load a picture from a Base64-encoded string and display it.
The example code creates a WPF window inviting you to the upcoming PowerShell Conference EU 2016 taking place in April 2016 (where you can attend roughly 80 sessions and discuss PowerShell topics with more than 30 prominent speakers. More info can be found at www.psconf.eu, but do not wait for too long because seats are limited).
The window displays the official conference logo yet does not require a separate picture file. Instead, the image is embedded into the script and loaded directly into memory.
The embedded picture at the beginning of the script is pretty large. The key part is the function Convert-Base64Bitmap2Picture below the Base64-encoded string. It accepts the Base64-encoded text and returns a bitmap object. This object can then be set as the source of any WPF image control.
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Streams help sort out information because streams can be muted. In fact, some streams are muted by default. Here is a sample function called Test-Stream. When you run it, it sends information to all seven streams.Please note: Write-Information was added in PowerShell 5.0. Remove the call to Write-Information from the sample if you want to run it in older PowerShell versions!
function Test-Stream { #region These are all the same and define return values 'Return Value 1' echo 'Return Value 2' 'Return Value 3' | Write-Output #endregion Write-Verbose 'Additional Information' Write-Debug 'Developer Information' Write-Host 'Mandatory User Information' Write-Warning 'Warning Information' Write-Error 'Error Information' # new in PowerShell 5.0 Write-Information 'Auxiliary Information' }Here is what you will most likely see when you run Test-Stream:
PS C:\> Test-Stream Return Value 1 Return Value 2 Return Value 3 Mandatory User Information WARNING: Warning Information Test-Stream : Error Information At line:1 char:1 + Test-Stream + ~~~~~~~~~~~ + CategoryInfo : NotSpecified: (:) [Write-Error]]> + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException,Test-Stream PS C:\> $result = Test-Stream Mandatory User Information WARNING: Warning Information Test-Stream : Error Information At line:1 char:1 + Test-Stream + ~~~~~~~~~~~ + CategoryInfo : NotSpecified: (:) [Write-Error], WriteErrorException + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException,Test-Stream PS C:\> $result Return Value 1 Return Value 2 Return Value 3 PS C:\>As you can see, echo and Write-Output work the same, and in fact are the same (because echo is an alias for Write-Output). They define the return value(s). They can be assigned to a variable. The same is true for unassigned values that your function leaves behind: they go to Write-Output as well.
Write-Host sends text output directly to the console, so it is guaranteed to be always visible. This cmdlet should be used for messages to the user.
The remaining streams are silent. To see the output from the remaining streams, you need to enable them first:
$VerbosePreference = 'Continue' $DebugPreference = 'Continue' $InformationPreference = 'Continue'Once you did this, Test-Stream produces output like this:
PS C:\> Test-Stream Return Value 1 Return Value 2 Return Value 3 VERBOSE: Additional Information DEBUG: Developer Information Mandatory User Information Auxiliary InformationTo restore the default values, reset the preference variables:
$VerbosePreference = 'SilentlyContinue' $DebugPreference = 'SilentlyContinue' $InformationPreference = 'SilentlyContinue'If you add the common parameters to your function, you can use -Verbose and -Debug when you call the function. Test-CommonParameter illustrates how you add common parameter support.
function Test-CommonParameter { [CmdletBinding()] param() "VerbosePreference = $VerbosePreference" "DebugPreference = $DebugPreference" }When you run Test-CommonParameter, you will immediately understand how the -Verbose and -Debug common parameters work: they simply change the local preference variables:
PS C:\> Test-CommonParameter VerbosePreference = SilentlyContinue DebugPreference = SilentlyContinue PS C:\> Test-CommonParameters -Debug -Verbose VerbosePreference = Continue DebugPreference = Inquire
