1. Reduce the exposure: use editing software (such as Photoshop) to adjust the exposure of photos to a suitable level, so as to make the images look softer and lower-key.
2. Reduce saturation: Adjust the saturation of photos to make their colors softer and lower-key. The brightness of flowers can be reduced appropriately to look more natural.
3. Adjust the color balance: Adjust the color balance of the photo to make it more in line with the low-key requirements. You can appropriately increase the hue of blue or green to make the image look softer.
4. Increase the dark corner effect: You can add the dark corner effect to darken the periphery of the image, make the flowers more prominent, and at the same time increase the low-key feeling of the photo.
5. Remove impurities: If there are impurities or unnecessary elements in the photo, you can remove them with retouching tools to make the photo cleaner and neater.