PIL Convert PNG or GIF with Transparency to JPG without

Question

I'm prototyping an image processor in Python 2.7 using PIL1.1.7 and I would like all images to end up in JPG. Input file types will include tiff,gif,png both with transparency and without. I've been trying to combine two scripts that I found that 1. convert other file types to JPG and 2. removing transparency by creating a blank white image and pasting the original image over the white background. My searches are being spammed with people seeking to generate or preserve transparency rather than the opposite.

I'm currently working with this:

#!/usr/bin/python
import os, glob
import Image

images = glob.glob("*.png")+glob.glob("*.gif")

for infile in images:
    f, e = os.path.splitext(infile)
    outfile = f + ".jpg"
    if infile != outfile:
        #try:
        im = Image.open(infile)
        # Create a new image with a solid color
        background = Image.new('RGBA', im.size, (255, 255, 255))
        # Paste the image on top of the background
        background.paste(im, im)
        #I suspect that the problem is the line below
        im = background.convert('RGB').convert('P', palette=Image.ADAPTIVE)
        im.save(outfile)
        #except IOError:
           # print "cannot convert", infile

Both scripts work in isolation, but as I have combined them I get a ValueError: Bad Transparency Mask.

Traceback (most recent call last):
File "pilhello.py", line 17, in <module>
background.paste(im, im)
File "/usr/lib/python2.7/dist-packages/PIL/Image.py", line 1101, in paste
self.im.paste(im, box, mask.im)
ValueError: bad transparency mask

I suspect that if I were to save a PNG without transparency I could then open that new file, and re-save it as a JPG, and delete the PNG that was written to disk, but I'm hoping that there is an elegant solution that I haven't found yet.

Why would you expect the problem is the "line below" when the code is barfing on the `.paste()` and not even getting to that line? — kindall, Oct 27 '11 at 04:06
This question here came later, but has all the answers: https://stackoverflow.com/a/33507138/2628864 — Vinícius M, Jun 16 '20 at 17:24

kindall · Accepted Answer · 2011-10-27T13:53:42.233

34

Make your background RGB, not RGBA. And remove the later conversion of the background to RGB, of course, since it's already in that mode. This worked for me with a test image I created:

from PIL import Image
im = Image.open(r"C:\jk.png")
bg = Image.new("RGB", im.size, (255,255,255))
bg.paste(im,im)
bg.save(r"C:\jk2.jpg")

edited Oct 27 '11 at 13:53

answered Oct 27 '11 at 04:15

kindall

178,883
35
278
309

4

It fails on http://img293.imageshack.us/img293/1434/teslahv5.png, what can I do to fix it? – Eugene Nagorny May 30 '12 at 15:49
I think the line bg.paste(im,im) needs to be bg.paste(im,mask=im) – Ramast Mar 26 '14 at 13:15
2

Got '*** ValueError: bad transparency mask' for mask=im – Sandeep Sep 22 '14 at 22:17
And using the solution above still gives '*** ValueError: bad transparency mask'. Not sure why – Sandeep Sep 22 '14 at 22:27
Perhaps late, but try `bg.paste(im, mask=im.split()[3])` – Jens Oct 28 '15 at 04:17
Over HERE folks: https://stackoverflow.com/a/33507138/2628864 – Vinícius M Jun 16 '20 at 17:23

score 8 · Answer 2 · answered Jan 04 '12 at 00:29

image=Image.open('file.png')
non_transparent=Image.new('RGBA',image.size,(255,255,255,255))
non_transparent.paste(image,(0,0),image)

The key is to make the mask (for the paste) the image itself.

This should work on those images that have "soft edges" (where the alpha transparency is set to not be 0 or 255)

score 5 · Answer 3 · answered Oct 27 '11 at 04:12

5

The following works for me on this image

f, e = os.path.splitext(infile)
print infile
outfile = f + ".jpg"
if infile != outfile:
    im = Image.open(infile)
    im.convert('RGB').save(outfile, 'JPEG')

answered Oct 27 '11 at 04:12

uncreative

1,436
9
14

I tried this approach at first. Just converting directly to RGB mode works with a hard-edged mask, but can fail pretty nastily with a soft-edged mask. – kindall Oct 27 '11 at 04:20
Can you provide a link to an image where it fails? I can see if I can get it to work – uncreative Oct 27 '11 at 04:21
[Here's the one](http://mac.jerrykindall.com:81/pil/jk.png) I made to play with this. And [here's the result](http://mac.jerrykindall.com:81/pil/jk_bad.png) of just stripping off the alpha channel. – kindall Oct 27 '11 at 04:28

score 1 · Answer 4 · answered Feb 17 '22 at 16:32

from PIL import Image


def png2jpg(file_name:str, trans_color: tuple):
    """
    convert png file to jpg file
    :param file_name: png file name
    :param trans_color: set transparent color in jpg image
    :return:
    """
    with Image.open(file_name) as im:
        image = im.convert("RGBA")
        datas = image.getdata()
        newData = []
        for item in datas:
            if item[3] == 0:  # if transparent
                newData.append(trans_color)  # set transparent color in jpg
            else:
                newData.append(tuple(item[:3]))
        image = Image.new("RGB", im.size)
        image.getdata()
        image.putdata(newData)
        image.save('{}.jpg'.format(file_name))

To convert png to jpg run png2jpg("try.png", (255,255,255))

Result:

PIL Convert PNG or GIF with Transparency to JPG without

4 Answers4

Linked

Related