Media: improve doc blocks for PNG handling in Imagick.

These changes were inadvertently omitted from [60667].

Props adamsilverstein.



git-svn-id: https://develop.svn.wordpress.org/trunk@60669 602fd350-edb4-49c9-b593-d223f7449a82

Author: adamsilverstein

src/wp-includes/class-wp-image-editor-imagick.php

@@ -444,21 +444,19 @@ protected function thumbnail_image( $dst_w, $dst_h, $filter_name = 'FILTER_TRIAN
 		}
 
 		try {
-			/*
-			 * We need to perform some special handling for certain types of images:
+			/**
+			 * Special handling for certain types of PNG images:
 			 * 1. For PNG images, we need to specify compression settings and remove unneeded chunks.
 			 * 2. For indexed PNG images, the number of colors must not exceed 256.
 			 * 3. For indexed PNG images with an alpha channel, the tRNS chunk must be preserved.
-			 * 4. For indexed PNG images with true alpha transparency (an alpha channel > 1 bit),
-			 *    we need to avoid saving the image using ImageMagick's 'png8' format,
-			 *    because that supports only binary (1 bit) transparency.
+			 * 4. For indexed PNG images with true alpha transparency (an alpha channel > 1 bit), we need to avoid saving
+			 * the image using ImageMagick's 'png8' format,  because that supports only binary (1 bit) transparency.
+			 *
+			 * For #4 we want to check whether the image has a 1-bit alpha channel before resizing,  because resizing
+			 * may cause the number of alpha values to multiply due to antialiasing. If the original image had only a
+			 * 1-bit alpha channel, then a 1-bit alpha channel should be good enough for the resized images.
 			 *
-			 * For #4 we want to check whether the image has a 1-bit alpha channel before resizing,
-			 * because resizing may cause the number of alpha values to multiply due to antialiasing.
-			 * (We're assuming that, if the original image had only a 1-bit alpha channel,
-			 * then a 1-bit alpha channel should be good enough for the resized images too.)
-			 * So we're going to perform all the necessary checks before resizing the image
-			 * and store the results in variables for later use.
+			 * Perform all the necessary checks before resizing the image and store the results in variables for later use.
 			 */
 			$is_png                                      = false;
 			$is_indexed_png                              = false;