Check images for true alpha transparency #8933
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Because ImageMagick cannot save images with true alpha transparency in indexed PNG format, we need to check whether an image has true alpha transparency before telling ImageMagick to use the png8 (indexed) format. See https://core.trac.wordpress.org/ticket/63448
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The additional comments are based on a suggestion from @SirLouen: https://core.trac.wordpress.org/ticket/63448#comment:89 (But I have added a bit more detail.)
| $is_png = false; | ||
| $is_indexed_png = false; | ||
| $is_indexed_png_with_alpha_channel = false; | ||
| $is_indexed_png_with_true_alpha_transparency = false; |
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can we add a comment here indicating the meaning of true alpha channel (vs alpha channel)
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I've added a comment which explains the purpose of all these variables (and mentions what "true alpha" means here). Does that make things clearer?
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yes, thanks. I will update the language slightly.
| && defined( 'Imagick::CHANNEL_ALPHA' ) | ||
| ) { | ||
| $alpha_channel_depth = $this->image->getImageChannelDepth( Imagick::CHANNEL_ALPHA ); | ||
| if ( $alpha_channel_depth > 1 ) { |
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this conditional can be included in the if block above
Because ImageMagick cannot save images with true alpha transparency in indexed PNG format, we need to check whether an image has true alpha transparency before telling ImageMagick to use the png8 (indexed) format.
Trac ticket: https://core.trac.wordpress.org/ticket/63448
This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.