-grayscale documentation

[fmw42]

The page at http://www.imagemagick.org/script/comma ... #grayscale is wrong, I believe, since -colorspace gray is currently non-linear.

The page says:

Code: Select all

This will use one of the -intensity methods to convert the given image into a linear-grayscale image.

For example, to convert an image to (linear) Rec709Luminance grayscale, type:

convert in.png -grayscale Rec709Luminance out.png
which is equivalent to:

convert in.png -colorspace gray out.png
Similarly, to convert an image to (non-linear) Rec709Luma grayscale, type:

convert in.png -grayscale Rec709Luma out.png
which is equivalent to:

convert in.png -set colorspace RGB -colorspace gray out.png

But should say

Code: Select all

This will use one of the -intensity methods to convert the given image into a grayscale image.

For example, to convert an image to (linear) Rec709Luminance grayscale, type:

convert in.png -grayscale Rec709Luminance out.png
which is equivalent to:

convert in.png -set colorspace RGB -colorspace gray out.png

Similarly, to convert an image to (non-linear) Rec709Luma grayscale, type:

convert in.png -grayscale Rec709Luma out.png
which is equivalent to:

convert in.png -colorspace gray out.png