Resize image with ImageMagick and set background color

Question

I want to resize a 100x200 image to a new 400x400 image with ImageMagick.

So far I have the following command:

convert in.png -resize^ 400x400 -compose Copy -gravity center -extent 400x400 out.png

Now I want to read the color from the top, left pixel of the in.png and set it as background color of the out.png.

Does anybody know how to do it?

Answer 1

You can get the colour of the pixel ar top-left corner (coordinates: 0,0) like this:

convert in.png -colorspace rgb -format "%[pixel:p{0,0}]" info:

Output:

rgb(201,200,206)

If you are on OSX/Linux/Unix you can capture that in a variable and use it to set the background like this:

c=$(convert in.png -colorspace rgb -format "%[pixel:p{0,0}]" info:)
convert in.png -background "$c" ...

So, if we start with this image:

and do this:

c=$(convert in.png -colorspace rgb -format "%[pixel:p{0,0}]" info:)

echo $c           # Check that puppy's colour
rgb(255,0,0)      # Yep, it's red

convert -background "$c" in.png -resize 400x400 -gravity center -extent 400x400 out.png

we will get this:

If you are unfortunate enough to be on Windows, you will have to do some unintelligible stuff with FOR /F that you will need to work out for yourself from here.