Adjust Image Contrast
Adjust Image Contrast uses the browser contrast(n%) filter, defaulting to 110%. Values above 100 increase separation around a midpoint and values below 100 reduce it; zero or invalid input falls back to 100 in this implementation. Strong contrast can clip shadows and highlights and does not provide tone-curve or local-contrast control.
Runs locally — files stay on your deviceWhat value leaves contrast nominally unchanged?
100%.
Global contrast changes tonal separation across the image
A simple contrast filter transforms each rendered channel globally. It cannot distinguish subjects, regions, or lighting zones.
How it works
Canvas sets contrast to the entered percentage, draws the bitmap, and writes a PNG at original pixel dimensions.
Key concepts
Contrast can clip both ends
Dark and bright pixels can lose distinct values.
Global changes affect skin, sky, text, and noise together
There are no masks.
When to use it
- Create a quick punchier derivative.
- Reduce tonal separation for a flat effect.
- Compare simple global settings.
When not to use it
- Do not use for local contrast or curves.
- Do not expect dynamic-range recovery.
- Do not enter zero expecting a uniform middle gray.
Worked examples
Increase
- Input
120%- Expected output
Higher global contrast
Tones spread farther apart.
Decrease
- Input
60%- Expected output
Flatter rendering
Tones move closer together.
Zero
- Input
0%- Expected output
100% fallback
The falsy numeric value is replaced.
Common mistakes
Expecting zero contrast
Zero falls back to neutral. Correction: Use a small positive value if needed.
Ignoring clipping
Extremes can lose texture. Correction: Inspect shadows and highlights.
Confusing clarity with contrast
Local detail enhancement is different. Correction: Use a local-contrast tool.
Best practices
- Adjust moderately.
- Check critical tonal regions.
- Compare with the source at equal zoom.
Related operations and differences
Adjust Image Saturation
Choose Adjust Image Saturation when you need to control the intensity of image colors.; use Adjust Image Contrast specifically for contrast.
Add Text Watermark to Image
Choose Add Text Watermark to Image when you need to place a text watermark in the lower-right corner.; use Adjust Image Contrast specifically for contrast.
Adjust Image Brightness
Choose Adjust Image Brightness when you need to increase or decrease image brightness.; use Adjust Image Contrast specifically for contrast.
Crop Image
Choose Crop Image when you need to crop an image to an exact local pixel rectangle.; use Adjust Image Contrast specifically for contrast.
Flip Image Horizontally
Choose Flip Image Horizontally when you need to mirror an image from left to right.; use Adjust Image Contrast specifically for contrast.
Flip Image Vertically
Choose Flip Image Vertically when you need to mirror an image from top to bottom.; use Adjust Image Contrast specifically for contrast.
Limitations and privacy
- Global canvas contrast only.
- Zero/invalid becomes 100%.
- No curves, masks, histogram, local contrast, preview, or clipping indicators.
Selected images are decoded and processed locally in this browser.
Frequently asked questions
What is neutral?
100%.
Does 0% flatten the image?
Not here; it falls back to 100%.
Can regions be masked?
No.
Are dimensions changed?
No.