ImageMagick - 如何更改目标颜色的饱和度？

Question

使用ImageMagick转换，如何调整特定色调的饱和度？ （以度为单位）

e.g。我增加了红色的饱和度（0度色调）。蓝色的颜色不会受到影响，但橙色也会稍微饱和，因为它紧挨着红色。

当然，我希望能够配置受影响的颜色宽度。

注意：请使用转换命令，而不是重定向到脚本。

PS：在 emcconville 的回答后澄清：

饱和度是渐进的：我们越接近匹配颜色，滤镜应用的越多。基本上它是在Photoshop中完成的。看截图 - 对不起它是法语，Teinte意味着Hue。您可以在底栏中查看和调整匹配颜色的范围，范围在8到90之间（和318到255），过滤器是渐进式的。

Answer 1

The Color Modification guide offers a few examples

Here's an example that will drop the saturation by half if the hue is close to red (0°)

convert rose: \( +clone -modulate 100,50 \) \
        -fx '(u.hue < 0.1 || u.hue > 0.9)? v : u' out.png

This works by copying the first image (+clone), and alter the saturation (-modulate) of the copied image. For the -fx part, u is the first image, and v is the second. If the hue of the first image matches our color, return the second image, else return the first.

Note: Red is 0°, so we need a logical OR (||), but if we're attempting to match another color, not overlapping zero, use the logical AND (&&).

example with blue

-fx '(u.hue < 0.69 && u.hue > 0.63) ? v : u'

Additional Answer

The same -fx approach can be used by calculating the linear scale -- like this answer, or here. Below is a similar (but not accurate) equation, and shows how to isolate the saturation channel.

convert rose: -colorspace HSL \
  \( +clone -colorspace sRGB \
     -fx '(hue < 0.1)?saturation+((1-(hue+0.1)*10%1)/10):(hue > 0.9)?saturation+(((hue-0.1) * 10)%1):saturation-(abs(0.5-hue))' \
  \) \
  -compose CopyGreen -composite \
  -colorspace sRGB \
  out.png

The -compose CopyGreen -composite seems odd, but what that is really doing is taking the image generated with -fx, and applying that as the second color channel (saturation).

Also experiment with -color-matrix, -contrast-stretch, & -linear-stretch.