vipsthumbnail problem with alpha transparent png about libvips HOT 14 CLOSED

I've added a @background arg to save: jcupitt@b21c47b

Use like this:

$ vipsthumbnail rtd-img.png -o x.jpg[background=255]

It'll be in 7.42.

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Thank you for the report. It was saving RGBA as CMYK jpg, with comical results. Here's a fix for master:

jcupitt@f07fb25

I'll try to backport to 7.28.

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7.28 now seems to handle this correctly. I added a thing to flatten RGBA to RGB more carefully as well: before it was just throwing away the A channel, now it does a proper blend with a background colour.

I'll do another 7.28 release in a few days, or you could try building from git.

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holy shit, this was the most professionally done response with instant supplied fix in history of github.

mind = blown.

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Embarrassment is a great motivator :-(

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I think this is back. I'm using vips-7.38.5 and vipsthumbnail converts transparent pngs to black background. Same thing also happens if I use batch_image_convert for the conversion.

folder with original png and thumbnailed jpg: https://www.dropbox.com/sh/pxfmd18pd4u2vin/AACUjmgWT_guVp90ZDCvuKzma?lst

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That's expected behaviour: it flattens the image with a black background.

There maybe should be something to let you pick another colour, I suppose white will be the other common one. I'll have a look.

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Awesome, thanks.

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I don't understand that being expected behavior. How do I preserve the transparency?

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Hi @franklinwise, this is if you thumbnail to a jpg image (the default). Jpeg does not support transparency, so you need to flatten it out with a background.

If you thumbnail to something like png, which does support transparency, it'll be kept.

vipsthumbnail file.png --format tn_%s.png

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@jcupitt - Awesome, thanks. I didn't realize that jpeg was the default.

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I have 7.42.2 I am also having same issue and i am converting from png to jpeg only how can i preserve the transparency ?

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And this doesn't seem to work vipsthumbnail rtd-img.png -o x.jpg[background=255] with me.

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never mind it works i was using zsh and i had to give it inside quote Thank u :)

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