diff --git a/MANUAL.txt b/MANUAL.txt index c23a4fab..cfd711fb 100644 --- a/MANUAL.txt +++ b/MANUAL.txt @@ -70,8 +70,8 @@ Options: -a, --alpha Perform additional optimization on images with an alpha channel, by altering the color values of fully transparent pixels. This is generally recommended for better compression, - but take care as this is technically a lossy transformation and may be unsuitable for some - applications. + but take care as while this is “visually lossless”, it is technically a lossy + transformation and may be unsuitable for some applications. -i, --interlace Set the PNG interlacing type, where is one of: @@ -86,8 +86,13 @@ Options: [default: 0] --scale16 - Forcibly reduce 16-bit images to 8-bit. Reduction is performed by scaling the values, such - that e.g. 0x00FF is reduced to 0x01 rather than 0x00. + Forcibly reduce images with 16 bits per channel to 8 bits per channel. This is a lossy + operation but can provide significant savings when you have no need for higher depth. + Reduction is performed by scaling the values such that, e.g. 0x00FF is reduced to 0x01 + rather than 0x00. + + Without this flag, 16-bit images will only be reduced in depth if it can be done + losslessly. -v, --verbose... Run in verbose mode (use twice to increase verbosity) @@ -96,7 +101,7 @@ Options: Run in quiet mode -f, --filters - Peform compression trials with each of the given filter types. You can specify a + Perform compression trials with each of the given filter types. You can specify a comma-separated list, or a range of values. E.g. '-f 0-3' is the same as '-f 0,1,2,3'. PNG delta filters (apply the same filter to every line) diff --git a/src/main.rs b/src/main.rs index 74e68071..94e2f9b4 100644 --- a/src/main.rs +++ b/src/main.rs @@ -186,8 +186,8 @@ depth is changed, regardless of any options set.", .long_help("\ Perform additional optimization on images with an alpha channel, by altering the color \ values of fully transparent pixels. This is generally recommended for better compression, \ -but take care as this is technically a lossy transformation and may be unsuitable for some \ -applications.") +but take care as while this is “visually lossless”, it is technically a lossy \ +transformation and may be unsuitable for some applications.") .short('a') .long("alpha") .action(ArgAction::SetTrue), @@ -213,10 +213,15 @@ believe the benefits outweigh the costs for your use case.") ) .arg( Arg::new("scale16") - .help("Forcibly reduce 16-bit images to 8-bit") + .help("Forcibly reduce 16-bit images to 8-bit (lossy)") .long_help("\ -Forcibly reduce 16-bit images to 8-bit. Reduction is performed by scaling the values, such \ -that e.g. 0x00FF is reduced to 0x01 rather than 0x00.") +Forcibly reduce images with 16 bits per channel to 8 bits per channel. This is a lossy \ +operation but can provide significant savings when you have no need for higher depth. \ +Reduction is performed by scaling the values such that, e.g. 0x00FF is reduced to 0x01 \ +rather than 0x00. + +Without this flag, 16-bit images will only be reduced in depth if it can be done \ +losslessly.") .long("scale16") .action(ArgAction::SetTrue), ) @@ -240,7 +245,7 @@ that e.g. 0x00FF is reduced to 0x01 rather than 0x00.") Arg::new("filters") .help(format!("Filters to try (0-{}; see '--help' for details)", RowFilter::LAST)) .long_help("\ -Peform compression trials with each of the given filter types. You can specify a \ +Perform compression trials with each of the given filter types. You can specify a \ comma-separated list, or a range of values. E.g. '-f 0-3' is the same as '-f 0,1,2,3'. PNG delta filters (apply the same filter to every line)