something about webui parameter denoising_strength

[D222097]

Hi, everyone, I'm curious about parameter denoising_strength in webui. Although documentation is available to get the information, I still want to understand how it works with codes. Unfortunately I didn't find it, denoising_strength is passed to function StableDiffusionProcessingTxt2Img/StableDiffusionProcessingImg2Img, and then there seems to be no follow-up.
Besides, for img2img, there is a parameter strength in diffusers which value in [0.0, 1.0] , it works as :

is_strength_max = strength == 1.0
...
noise = randn_tensor(shape, generator=generator, device=device, dtype=dtype)
latents = noise if is_strength_max else self.scheduler.add_noise(image_latents, noise, timestep)

It works much like denoising_strength:"Determines how little respect the algorithm should have for image's content. At 0, nothing will change, and at 1 you'll get an unrelated image. With values below 1.0, processing will take less steps than the Sampling Steps slider specifies.", I wonder if denoising_strength in webui and strength in diffusers work in exactly the same way, and why denoising_strength is also set in txt2img.

[w-e-w]

With values below 1.0, processing will take less steps than the Sampling Steps slider specifies.

Settinngs > img2img > With img2img, do exactly the amount of steps the slider specifies. disabled by default

https://github.com/AUTOMATIC1111/stable-diffusion-webui/blame/cf2772fab0af5573da775e7437e6acdca424f26e/modules/sd_samplers_common.py#L22-L31