Error in converting a PDF to a PNG in ImageMagick

Question

I use Imagemagick convert to convert pdf file to png as follows:

Magick convert -density 300 PointOnLine.pdf -quality 90 PointOnLine.png

It gives warning:

convert: profile 'icc': 'RGB ': RGB color space not permitted on grayscale PNG `PointOnLine.png' @ warning/png.c/MagickPNGWarningHandler/1744.

And png image created is all black. However, convert to jpg image is fine. What is the problem? Thanks.

Solution 1

Try adding -colorspace RGB before the outfile name.

convert -density 300 PointOnLine.pdf -quality 90 -colorspace RGB PointOnLine.png

Solution 2

The documentation says this:

PNG RW Portable Network Graphics Requires libpng-1.0.11 or later, libpng-1.2.5 or later recommended. The PNG specification does not support pixels-per-inch units, only pixels-per-centimeter. To avoid reading a particular associated image profile, use -define profile:skip=name (e.g. profile:skip=ICC).

So try adding -define profile:skip=ICC (or skip="*") before the outfile name.

See also: documentation on the define command

Comments

[hermes]

No, after setting -define profile:skip=ICC, image is still dark. But if convert to jpg and then to png, it is ok, but background is dark. The same warning happens.

[user74094]

Nice. For me the white background became transparent, but this can still be used.

[DannyB]

Note that this solution, although removing the warning, also changes the shades of gray in the generated PNG.

[DannyB]

This works better than setting -colorspace RGB - for me it removes the warning and does not alter the shades of gray of the output.

[Torsten Bronger]

I don’t want to put the validity of this answer in question but I just don’t understand the connection between “pixels per centimetre/inch” and a colour profile. Can somebody explain this to me?