I use Imagemagick convert to convert pdf file to png as follows:
Magick convert -density 300 PointOnLine.pdf -quality 90 PointOnLine.png
It gives me the following 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.
Update: After adding -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 is still there. What is the problem? Thanks.
The following works for me without error in ImageMagick 7.0.7.22 Q16 Mac OSX Sierra with Ghostscript 9.21 and libpng @1.6.34_0. Your PDF has an alpha channel, so you might want to flatten it.
magick -density 300 PointOnLine.pdf -flatten -quality 90 result.png
This also works without error, but leaves the alpha channel in the png, though you won't see it here until you extract the image:
magick -density 300 PointOnLine.pdf -quality 90 result2.png
Note that in IM 7 you should just use magick and not magick convert.
Check that you are using a current version of Ghostscript and libpng, if you do not get the same results.
Your delegates.xml file for PS:alpha should show sDEVICE=pngalpha rather than pnmraw as follows.
<delegate decode="ps:alpha" stealth="True" command=""gs" -sstdout=%%stderr -dQUIET -dSAFER -dBATCH -dNOPAUSE -dNOPROMPT -dMaxBitmap=500000000 -dAlignToPixels=0 -dGridFitTT=2 "-sDEVICE=pngalpha" -dTextAlphaBits=%u -dGraphicsAlphaBits=%u "-r%s" %s "-sOutputFile=%s" "-f%s" "-f%s""/>
USER REQUESTED RESULTING IMAGES THAT I POSTED TO BE REMOVED!