Legacy ImageMagick Discussions Archive

Hello together,

ich have severall tiff Images which i want to convert to jpg

these Tiff Files can either have a transparent Background and/or an additional Alpha Channel

Example File with Transparent background: http://home.arcor.de/durius.obsidian/transparent.tif
Example File with Alpha Channel: http://home.arcor.de/durius.obsidian/alpha2.tif

I started with a simple conversion: convert transparent.tif -resize 400x400 transparent.jpg http://home.arcor.de/durius.obsidian/transparent.jpg

Problem: Black Background. Ok i set background to white:

convert transparent.tif -background white -flatten -resize 400x400 transparent_white.jpg http://home.arcor.de/durius.obsidian/tr ... _white.jpg

looks fine, next image:

convert alpha2.tif -background white -resize 400x400 alpha_white.jpg http://home.arcor.de/durius.obsidian/alpha_white.jpg

Problem: the alphaChannel i used as mask, ok so no alpha channel:

convert -alpha off alpha2.tif -background white -resize 400x400 alpha_white_alpha_off.jpg http://home.arcor.de/durius.obsidian/al ... ha_off.jpg

looks fine, but can this command be used for the first image?

convert -alpha off transparent.tif -background white -resize 400x400 transparant_white_alpha_off.jpg http://home.arcor.de/durius.obsidian/tr ... ha_off.jpg


Problem: Background is black again. So my question: Is there a command line that would work on both images?


I must admit, that the transparent.tif is possible broken, because with other tiff Images with transparancies i get better results. Or have i found a missing feature?




ImageMagick version is:

convert -version
Version: ImageMagick 6.6.1-4 2010-04-20 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2010 ImageMagick Studio LLC
Features: OpenMP

JPG does NOT support transparency. Use GIF or PNG. If you want jpg, then you have to do what you did making the background white

convert alpha2.tif -resize 400x400 -background white -flatten alpha2_white.jpg
convert transparent.tif -resize 400x400 -background white -flatten transparent_white.jpg

otherwise

convert alpha2.tif -resize 400x400 alpha2.png
convert transparent.tif -resize 400x400 transparent.png

will leave it transparent

Well this is funny

while convert transparent.tif -resize 400x400 transparent.png http://home.arcor.de/durius.obsidian/transparent.png

has a transparent background

convert transparent.tif -resize 400x400 transparent2.tif http://home.arcor.de/durius.obsidian/transparent2.tif

has a black background.

I also uploaded: convert alpha2.tif -resize 400x400 -background white -flatten alpha2_white.jpg http://home.arcor.de/durius.obsidian/alpha2_white.jpg sorry, i forgot the flatten option but this still doen't look anything near the original image

I will experiment with the png output.

looks the same to me.

this works fine for me on IM 6.6.1-4 Q16 Mac OSX Tiger

convert transparent.tif -resize 400x400 transparent_small.tif

and the result is still transparent.

What version of IM are you using, if old perhaps upgrade.

Im Version is: 6.6.1-4 Q16 Linux x86_64
Libtiff is : 3.8.2-7

how are you viewing the result. perhaps the viewer does not know how to deal with transparency

http://home.arcor.de/durius.obsidian/transparent2.tif
has a black background.

No. Downloading and examining with Gimp shows it has a transparent black background. (The background is transparent. Using eyedropper or anti-erase reveals black.)

Well i guess i put too much trust in photoshop cs3.

The question remains: can i convert both images with one command line to jpg with white background?

I'm not sure it is possible.

The same command can replace transparency with white (more accurately, it places the image over a white background, so the white shows through fully- or partially-transparent pixels).

convert transparent.tif -resize 400x400 -background white -flatten transparent_w.jpg
convert alpha2.tif -resize 400x400 -background white -flatten alpha2_w.jpg

Note that alpha2.tif has a clipping path, which the above commands ignore. In this case it makes no difference, but you could safely add "-clip" before "-background" to both commands.

I mad a screenshot alpha2.tif and alpha2_w.jpg side by side:

http://home.arcor.de/durius.obsidian/result.png

the bottom part is missing. So far i suspect the alpha channel "Alpha 1" is set to white, destroying parts of the image. Thas is what i descriped earlier as is said : "alphaChannel i used as mask"

What program did you use to display the images?

Using Gimp on alpha2.tif, I find the pixels of the jar (and lettering and shadow) are transparent.

But Gimp gives a warning: "alpha channel type not defined for file D:\web\im\alpha2.tif. Assuming alpha is not premultiplied". This is, I think, the tiff:alpha:associated/unassociated flag.

Again Photoshop CS3.

I also made a screenshoot displaying channel "Alpha 1": http://home.arcor.de/durius.obsidian/alpha2_ps_view.png

You have a useless alpha channel. Just turn it off.

convert alpha2.tif -alpha off alpha2_aoff.tif

Unless all you want is the lid. then

convert alpha2.tif -background white -flatten alpha2_white.tif

Yes, Gimp shows the same: the lid is opaque, and the rest is transparent.

i really would love to just turn off the alpha channel. But then the first image gets a black background again:

Problem: the alphaChannel i used as mask, ok so no alpha channel:

convert -alpha off alpha2.tif -background white -resize 400x400 alpha_white_alpha_off.jpg http://home.arcor.de/durius.obsidian/al ... ha_off.jpg

looks fine, but can this command be used for the first image?

convert -alpha off transparent.tif -background white -resize 400x400 transparant_white_alpha_off.jpg http://home.arcor.de/durius.obsidian/tr ... ha_off.jpg

and i need it one command line for both images, if it can' t be done; well