imagemagick：如何在绘制矩形命令中使用 %[fx:...] 运算符？

Question

I can do this to draw a red rectangle on an image:

convert original.png -fill red -draw "rectangle 10,20 150,40" result.png

The 150,40 is the right bottom coordinate. However if I use the %[fx:...] operator in there, like so:

convert original.png -fill red -draw "rectangle 10,20 %[fx:w-30],40" result.png

The %[fx:w-30] is supposed to evalute to the image's width minus 30.

However I'm getting an error:

convert: non-conforming drawing primitive definition `rectangle' @ error/draw.c/DrawImage/4227.

I have also tried single quotes (') instead of double (") but that made no difference.

My imagemagick version is 7.0.7-36.

What am I doing wrong? What's the correct way of using the %[fx:...] operator in the above example?

Answer 1

感谢@GeeMack 解决方案是：使用magick而不是convert ，所以它变成：

magick original.png -fill red -draw "rectangle 10,20 %[fx:w-30],40" result.png

Answer 2

If you're still on ImageMagick 6, you can use the identify command to output a formatted string and then use that in the convert command. Using shell syntax, this can be expressed as follows:

convert original.png -fill red -draw "$(identify -format 'rectangle 10,20 %[fx:w-30],40' original.png)" result.png