Vector to PNG with alpha transparency problems

[rossmeissl]

Hello,

I'm having trouble converting a vector file to PNG while preserving alpha transparency. I've tried every possible combination of options I could find on the board, and still no luck.

I've tried starting with all 3 of these file types:

• EPS: http://banjo.brighterplanet.com/andy/motorcycle.eps
• PDF: http://banjo.brighterplanet.com/andy/motorcycle.pdf
• SVG: http://banjo.brighterplanet.com/andy/motorcycle.svg

The EPS and PDF always come out with a white background, despite trying the "-colorspace RGB," "-channel RGBA," and "-background none" tricks I have found here.

Here are some examples:

• convert -channel RGBA -colorspace RGB motorcycle.eps motorcycle-1.png
• convert motorcycle.eps -channel rgba -alpha On -background transparent motorcycle-2.png
• convert -background none motorcycle.eps -channel rgba -alpha On -background transparent motorcycle-3.png
• convert -background none motorcycle.pdf -background transparent -alpha On motorcycle-4.png
• convert -background none motorcycle.svg -background transparent -alpha On motorcycle.png

The closest I'm getting is with the SVG, but the resulting PNG inexplicably has a black background with 50% transparency behind the motorcycle.

Thanks in advance.

[magick]

Type

• convert -colorspace RGB motorcycle.eps motorcycle.png
  identify -verbose motorcycle.png

We get alpha statistics that show levels of transparency:

• alpha:
  min: 53713 (0.819608)
  max: 65535 (1)
  mean: 65525.1 (0.999848)
  standard deviation: 301.241 (0.00459664)
  kurtosis: 1034.93
  skewness: 31.6121

Do you get the same distribution for alpha?

[rossmeissl]

Code: Select all

    alpha:
      min: 53713 (0.819608)
      max: 65535 (1)
      mean: 65525.1 (0.999848)
      standard deviation: 301.241 (0.00459664)
      kurtosis: 1034.93
      skewness: 31.6121

Full output is at http://pastie.org/484496

[magick]

It appears that the conversion from EPS to PNG is preserving transparency as expected.

[rossmeissl]

Thanks for helping me with this!

Unfortunately, here's the output image that resulted from the commands you had me run:


http://banjo.brighterplanet.com/andy/motorcycle.png

As far as I can tell, it's not transparent.

[rossmeissl]

For comparison, when I use Illustrator's Save for Web, I get this:


http://banjo.brighterplanet.com/andy/mo ... narrow.png

[magick]

If the image is not rendered correctly, the bug is in Ghostscript or the Ghostscript pngalpha device. ImageMagick delegates Postscript rendering to Ghostscript with this command line:

• "gs" -q -dQUIET -dPARANOIDSAFER -dBATCH -dNOPAUSE -dNOPROMPT -dMaxBitmap=500000000 -dAlignToPixels=0 -dGridFitTT=0 "-sDEVICE=pngalpha" -dTextAlphaBits=4 -dGraphicsAlphaBits=4 "-r72x72" -g121x87 "-sOutputFile=/tmp/magick-XX1HoH3Z" "-f/tmp/magick-XXlMwZ7j" "-f/tmp/magick-XXBA8lcE"

[rossmeissl]

Any chance you could try that convert command on motorcycle.eps and make sure I'm not just crazy?

Thanks again.

[fmw42]

I downloaded your motorcycle.eps and did the following on IM 6.5.4-7 Q16 Mac OSX Tiger (with gs 8.61) and got:

convert motorcycle.eps motorcycle.png
Unknown device: bmpsep8
Unrecoverable error: undefined in .uninstallpagedevice
Operand stack:
defaultdevice
Unknown device: bmpsep8
Unrecoverable error: undefined in .uninstallpagedevice
Operand stack:
defaultdevice
convert: Postscript delegate failed `/var/tmp/magick-DWKZZyaR': No such file or directory @ ps.c/ReadPSImage/741.
convert: motorcycle.eps: invalid TIFF directory; tags are not sorted in ascending order. `TIFFReadDirectory' @ tiff.c/TIFFWarnings/525.

But it produces a partially transparent image:


But if I do
convert -colorspace rgb motorcycle.eps motorcycle2.png

I get a white background:

[rossmeissl]

Interesting. Dropping the colorspace argument like you did in your first test results in a white background for me, but runs without errors.

Does anybody have a test EPS with alpha transparency that has been verified to produce a correct PNG? I'd love to try it on my machine.

[fmw42]

I had this same problem/error in viewtopic.php?f=1&t=13753&hilit=bmpsep8 and viewtopic.php?f=3&t=13723&p=46762&hilit=bmpsep8#p46762

but so far no one has told me how to correct or avoid that error message. There must be some configuration that I need to do to fix it. Perhaps a GS upgrade. But I don't know for sure.

[rossmeissl]

For any Googlers landing here: rsvg performs SVG -> PNG-24 (with alpha transparency) conversions flawlessly.

[magick]

Use this command to perform SVG -> PNG-24 (with alpha transparency) conversions flawlessly:

• convert -background none motorcycle.svg motorcycle.png

Not sure why it did not work for you. We're using ImageMagick 6.5.2-7, the current release.

[rossmeissl]

Unfortunately, this is what I get from that command:


http://banjo.brighterplanet.com/andy/motorcycle-12.png