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tikz：用角度填充阴影颜色

发布于 2025-02-11 18:45:24 字数 1144 浏览 2 评论 0原文

目标：画一个半圆，并用线梯度填充，根据角度变化。例如，角度从θ= 0到θ=π，可以预期填充色调从红色到蓝色。

在tikz手册中（ https://tikz.dev/library-shadings ），阴影模式没有我在以下方面的需求：

选项shading =色轮似乎仅适用于圆而不是半圆。
选项shading =色轮在原点处呈现扭曲的颜色，而shading =色轮白色中心填充了原点的白色区域。
颜色whell似乎并不是真正的线路分级。

因此，有什么方法可以通过角度填充线梯度填充理想的半圆？

可以看到一个类似的示例在这里，但是需要一些更改：

可以预期。是半圆而不是象限。
填充的颜色优于按角度（或其结合角度）为渐变。

我尝试了以下代码，但是梯度模式似乎并不十分明显，而起源很棘手。

\documentclass[tikz, margin=5pt]{standalone}

\usepackage{tikz}
\usetikzlibrary{shadings}

\begin{document}

\begin{tikzpicture}
    \clip (0, 0) -- (1, 0) arc [start angle=0, end angle=180, radius=1cm] -- cycle ;
    \shade[shading=color wheel, shading angle=-60] (0, 0) circle (1cm) ;
\end{tikzpicture}

\end{document}

原文

Goal: Draw a semi-circle and fill it with line-gradient color that changes according to angle. For example, with angle from θ=0 to θ=π, it is expected that the filling color shades from red to blue.

In tikz manual (https://tikz.dev/library-shadings), the shading pattern does not statisfy my need in the following aspects:

The option shading = color wheel seems to only applicable to a circle rather than semi-circle.
The option shading = color wheel renders a distorted color at the origin, while shading=color wheel white center fills a white region at the origin.
The color whell seems not really line-gradient.

So, is there any way to make an ideal semi-circle with line-gradient color filling by angle?

A similar example can be seen here, but some changes are needed:

It is expected to be semi-circle rather than a quadrant.
The filled color is prefered to be gradient according the angle(or its consine).

I tried the following codes, but the gradient pattern seems not quite obvious, and the origin is screwy.

\documentclass[tikz, margin=5pt]{standalone}

\usepackage{tikz}
\usetikzlibrary{shadings}

\begin{document}

\begin{tikzpicture}
    \clip (0, 0) -- (1, 0) arc [start angle=0, end angle=180, radius=1cm] -- cycle ;
    \shade[shading=color wheel, shading angle=-60] (0, 0) circle (1cm) ;
\end{tikzpicture}

\end{document}

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落叶缤纷 2025-02-18 18:45:24

我建议使用pgfplots，然后您对颜色尺度的控制最多：

\documentclass[tikz, margin=5pt]{standalone}

\usepackage{pgfplots}
\pgfplotsset{compat=newest}

\begin{document}

\begin{tikzpicture}
\begin{axis}[
    axis equal=true,
    hide axis,     
    domain=0:180,
    domain y=0:1,
    view={0}{90},
    shader=interp,
    colormap={redblue}{
        color=(red)  color=(blue)
    },
    data cs=polar,
]
    \addplot3 [surf] {x};
\end{axis}
\end{tikzpicture}

\end{document}

I suggest to use pgfplots, then you have the most control over the colour scale:

\documentclass[tikz, margin=5pt]{standalone}

\usepackage{pgfplots}
\pgfplotsset{compat=newest}

\begin{document}

\begin{tikzpicture}
\begin{axis}[
    axis equal=true,
    hide axis,     
    domain=0:180,
    domain y=0:1,
    view={0}{90},
    shader=interp,
    colormap={redblue}{
        color=(red)  color=(blue)
    },
    data cs=polar,
]
    \addplot3 [surf] {x};
\end{axis}
\end{tikzpicture}

\end{document}