wrong colors applying watermark

[bartroby]

Hi,

we used ImageMagick in order to apply an image as watermark over a set of images (jpeg, png, ecc).
The watermark is 75% smaller than the original image.

Applying this image-watermark over some jpeg images, the colors of the image-result are different compared with the original image, also into the area outside of the watermark.
Why? How can we avoid to change colors?

We used the following command:

for /f %%A in ('convert %1 -ping -format "%%[fx:(h*0.75)/1637*100]" info:') do set y=%%A%%
composite -watermark 10%% -gravity center ( logo_opacita_50.png -resize %y% ) %1 newImg/%1

Thanks,

[fmw42]

you will need to post a link to your two images and output that look wrong. you can upload your images to any free hosting servers such as dropbox (public folder) and put a link here.

I suspect one of the images may be cmyk or have an alpha channel.