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| -rw-r--r-- | pngtopam.html | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/pngtopam.html b/pngtopam.html index 5e2add26..81858435 100644 --- a/pngtopam.html +++ b/pngtopam.html @@ -40,6 +40,16 @@ file. Otherwise, it creates a PPM file. Except that with the tuple type GRAYSCALE_ALPHA or RGB_ALPHA depending on whether the input has color or not. +<p>To convert in the other direction, use <b>pnmtopng</b> or +<b>pamrgbatopng</b>. The former is more powerful in almost every way, except +that only the latter can recognize transparency information in a PAM file, as +you might generate with <b>pngtopam -alphapam</b>. To use <b>pnmtopng</b> +with a PAM file with transparency, you can separate out the transparency +channel with <b>pamchannel</b> and feed it to <b>pnmtopng</b> separately. But +you may want to use <b>pngtopam -alpha</b> instead of <b>pngtopam +-alphapam</b> if you're going to be converting back. + + <H2 id="options">OPTIONS</H2> <DL COMPACT> @@ -62,6 +72,10 @@ format with tuple type of either GRAYSCALE_ALPHA (which has a depth of <b>-mix</b>. With none of them, <b>pngtopam</b> produces an image of the foreground of the input image and discards transparency information. +<p>Note that converting in the other direction, the <b>pamtopng</b> converter +won't recognize the transparency information you generate +with <b>-alphapam</b>, but <b>pamrgbatopng</b> will. + <P>This option was new in Netpbm 10.44 (September 2008). <DT><B>-alpha</B> |