EPS files are loaded without transparency

[yngvem]

EPS files can have transparency, and GhostScript have the option to keep it. However, if we use Pillow to open an EPS-file, then the alpha-channel is discarded. To my understanding, this is because Pillow is currently using the ppm (portable pixel map)-driver, which creates RGB-images, not RGBA-images.

I therefore propose to add an option to specify which driver to use with GhostScript (or add a flag that can be enabled to use the pngalpha driver instead of the ppmraw driver)

To my understanding, this can be fixed by modifying line 120 in src/PIL/EpsImagePlugin.py:

Pillow/src/PIL/EpsImagePlugin.py

Line 120 in 20b8a83

"-sDEVICE=ppmraw", # ppm driver

into

        "-sDEVICE=pngalpha",  # png driver

I made the change locally on my machine, and it seemed to work well.

What are your OS, Python and Pillow versions?

• OS: Windows 10
• Python: 3.8
• Pillow: 8.2.0

Endnote: Script to generate a postscript file and convert it with Pillow

import turtle
from PIL import Image

pen = turtle.Turtle()
for side in range(4):
    pen.forward(50)
    pen.right(90)

turtle.getscreen().getcanvas().postscript(file="square.eps")
img = Image.open('square.eps')
img.save("image.png")

[radarhere]

Thanks for finding a solution to your problem - I've created PR #5620

With that, you would

img = Image.open('square.eps')
img.load(transparency=True)
img.save("image.png")