i can not trim this kind of image

[magick]

Try adding -fuzz 15% to your command line. Fuzz permits close colors to match along with your target color.

[el_supremo]

The fuzz option won't help with this image. If you magnify it with an image viewer you will find that there is a margin along the top and left sides of the image that is two pixels wide consisting of various shades of grey pixels.

This is a screen grab of the top left corner of the image (I used Paint Shop Pro).
http://members.shaw.ca/saskbirder/newsletter_mag.png

I think trim will work if you first crop that margin out of the image.

Best Wishes
Pete

[magick]

You could also try -trim twice (e.g. -fuzz 15% -trim -trim).

[el_supremo]

I've played a bit with cropping and trimming that image and the margins are a bit more awkward than I thought.
In order for trim to work you have to crop a two pixel margin off the top, 5 pixels off the left margin and 5 off the bottom margin and then trim (with a fuzz of 15) reduces the image to 899x2269 from its original 982x4000.

Best Wishes
Pete

[anthony]

for more information on -trim see
http://www.cit.gu.edu.au/~anthony/graph ... crop/#trim

This includes fuzzy trims, trims with a specific color, and trim ignoring small features.

If anyone likes to add other techniques, please mail me.