Does Auto Contrast Image upload my file or text to Tool-You servers?

No. Auto Contrast Image runs in this browser tab. Files stay on the device. Limit note: Images. Luma min–max stretch. Output PNG. Max 20 MB.

Should I use Image Contrast instead of Auto Contrast Image?

Use Auto Contrast Image when you need Stretch luma min–max to 0–255. Use Image Contrast when you need Raise or lower contrast. They share a category (Images) but not the same job.

Auto Contrast Image

Stretch luma min–max to 0–255.

Stretches luminance min–max across RGB. Unlike Contrast Image this is histogram stretch, not a CSS contrast slider. Unlike High Contrast Image this uses the image range, not a fixed boost. Runs in the browser on a canvas.

What Auto Contrast Image does

Practical limit for Auto Contrast Image: Images. Luma min–max stretch. Output PNG. Max 20 MB. That is why output can differ from heavy desktop Images software. Read the tool-specific note again: Stretches luminance min–max across RGB. Unlike Contrast Image this is histogram stretch, not a CSS contrast slider. Unlike High Contrast Image this uses the image range, not a fixed boost. Runs in the browser on a canvas.

How to use Auto Contrast Image

Stay on this Auto Contrast Image page (/auto-contrast-image). Do not switch to Image Contrast unless you actually want Raise or lower contrast..
Add the file type Auto Contrast Image accepts. Hint from the path: auto contrast image. Stretch luma min–max to 0–255.
Set only the options that match Auto Contrast Image. Neighbor High Contrast Image does something else (Fixed 180% contrast, then PNG.). Tool note: Stretches luminance min–max across RGB. Unlike Contrast Image this is histogram stretch, not a CSS contrast slider. Unlike High Contrast Image this uses the image range, not a fixed boost. Runs in the browser on a canvas.
Run Auto Contrast Image in this tab. Browser memory still applies: Images. Luma min–max stretch. Output PNG. Max 20 MB.
Download or copy the result from Auto Contrast Image. If it is the wrong job, open Image Contrast instead.

When not to use Auto Contrast Image

Skip Auto Contrast Image when a neighbor tool matches better — start with Image Contrast or High Contrast Image — or when the description already warns the job will fail. In the tool’s own words: Stretches luminance min–max across RGB. Unlike Contrast Image this is histogram stretch, not a CSS contrast slider. Unlike High Contrast Image this uses the image range, not a fixed boost. Runs in the browser on a canvas.

Questions about Auto Contrast Image

What does Auto Contrast Image do that other Images pages on this site do not?: Stretches luminance min–max across RGB. Unlike Contrast Image this is histogram stretch, not a CSS contrast slider. Unlike High Contrast Image this uses the image range, not a fixed boost. Runs in the browser on a canvas. Short version: Stretch luma min–max to 0–255.
Does Auto Contrast Image upload my file or text to Tool-You servers?: No. Auto Contrast Image runs in this browser tab. Files stay on the device. Limit note: Images. Luma min–max stretch. Output PNG. Max 20 MB.
Should I use Image Contrast instead of Auto Contrast Image?: Use Auto Contrast Image when you need Stretch luma min–max to 0–255. Use Image Contrast when you need Raise or lower contrast. They share a category (Images) but not the same job.
What are the limits of Auto Contrast Image?: Images. Luma min–max stretch. Output PNG. Max 20 MB. Also: Stretches luminance min–max across RGB. Unlike Contrast Image this is histogram stretch, not a CSS contrast slider. Unlike High Contrast Image this uses the image range, not a fixed boost. Runs in the browser on a canvas.