Hook on spritesheet creation

[niksy]

Would it make sense to have hook when spritesheet is created?

One use case for this is image optimization with tool like imagemin where you could act on spritesheet image buffer and optimize it before it is saved (similar to transform for postcss-copy). This could be done in separate process like Gulp plugin or plugin like postcss-copy, but it seems like this could be nice addition to whole sprite generate process.

• One possible way for this hook: hook will expect promise resolve or reject like filterBy and groupBy where you would resolve with new spritesheet object.
• Or, maybe more in way of current implementation: adjust onSaveSpritesheet hook to have possibility of returning spritesheet object:
  • keep current implementation where if you return string it is final path for spritesheet
  • if you return promise with spritesheet object, use that as new spritesheet value
  • if you return promise with spritesheet path string, use that as new spritesheet final path (using promises is also keeping it within current async implementation)
• Maybe have option for optimization, where you would say you want to optimize your final image, and provide options to imagemin plugins.
  • Pros: simple and using known solution
  • Cons: not decoupled enough, not flexible enough if you want to have custom implementation for optimization algorithm

I’m leaning to solution number 2; open to modification and left to developers and how they want to handle final output.

---

Example:

sprites({
    // ...
    hooks: {
        onSaveSpritesheet: ( opts, spritesheet ) => {
            return imagemin.buffer(spritesheet.image, {
                plugins: [
                    imageminPngquant()
                ]
            }).then(( buff ) => {
                return Object.assign({}, spritesheet, {
                    image: buff
                });
            });
        }
    }
})

---

What do you think? Is this too much?

[vvasilev-]

I think that will be a nice addition to the plugin. Can you make a PR for this one?

[niksy]

Sure, will get on it as soon as possible!

[niksy]

@vvasilev- I’ve made the PR https://github.com/2createStudio/postcss-sprites/pull/70

Sorry this took so long :/