主题内容:当问到这幅画的时候，画家道出了一个他从未向别人透露过的秘密：画中的老农其实是他的父亲，这幅画见证了他对父亲的爱。；

翻译结果： When asked about the painting, the artist revealed a secret he had never shared with anyone: the old farmer in the painting is actually his father, and this painting bears witness to his love for his father.

解释：

1. 当问到这幅画的时候 - When asked about the painting（时间状语从句，主语：the artist，谓语：revealed）
   • "当...的时候" 表示在某个动作发生时，这里是在被问及画作时。
2. 画家道出了一个他从未向别人透露过的秘密 - the artist revealed a secret he had never shared with anyone
   • "道出" 这里指透露或揭示，"从未向别人透露过" 是一个过去完成时的从句，表示在现在之前一直未做的事情。
3. 画中的老农其实是他的父亲 - the old farmer in the painting is actually his father
   • "其实是" 表示揭示真实情况，"是" 为系动词。
4. 这幅画见证了他对父亲的爱 - this painting bears witness to his love for his father
   • "见证了" 表示证实或证明，"对父亲的爱" 是宾语，表明爱的接受者。

以上翻译保持了原文的情感和语境，并且避免了敏感词汇。