Filters
PreviewProxy supports four image filters: blur, grayscale, brightness, and contrast. Filters can be combined with each other and with resize or format conversion in a single request.
Blur
Apply a Gaussian blur to soften the image.
| Param | Type | Range | Description |
|---|---|---|---|
blur | float | 0-100 | Gaussian blur radius |
Higher values produce a stronger blur effect. A value of 0 means no blur.
/blur=5/https://example.com/img.jpg
| Value | Effect |
|---|---|
1-3 | Subtle softening |
5-10 | Noticeable blur |
20+ | Heavy blur / frosted glass effect |
Blur is useful for generating background placeholder images or creating a depth-of-field effect on thumbnails.
Grayscale
Convert the image to grayscale (black and white).
| Param | Type | Values | Description |
|---|---|---|---|
grayscale | bool | true or 1 | Convert to grayscale |
/grayscale=true/https://example.com/img.jpg
Both grayscale=true and grayscale=1 are equivalent.
Brightness
Adjust the brightness of the image.
| Param | Type | Range | Description |
|---|---|---|---|
bright | integer | -255 to 255 | Brightness adjustment (0 = no change) |
- Positive values make the image brighter
- Negative values make the image darker
0applies no change
/bright=50/https://example.com/img.jpg
/bright=-80/https://example.com/img.jpg
| Value | Effect |
|---|---|
255 | Maximum brightness (near white) |
50 | Moderately brighter |
0 | No change |
-50 | Moderately darker |
-255 | Maximum darkness (near black) |
Contrast
Adjust the contrast of the image.
| Param | Type | Range | Description |
|---|---|---|---|
contrast | integer | -255 to 255 | Contrast adjustment (0 = no change) |
- Positive values increase contrast (darks darker, lights lighter)
- Negative values decrease contrast (flatter, washed-out appearance)
0applies no change
/contrast=30/https://example.com/img.jpg
/contrast=-40/https://example.com/img.jpg
Combining Filters
All four filters can be combined with each other and with any other transform parameters in a single request.
Grayscale with blur
/grayscale,blur=2/https://example.com/img.jpg
Brightness and contrast together
/bright=20,contrast=40/https://example.com/img.jpg
Resize, convert format, grayscale, and blur in one request
/w=400,webp,grayscale,blur=2/https://example.com/img.jpg
Full combination
/800x600,cover,webp,q85,grayscale,bright=10,contrast=20,blur=1/https://example.com/img.jpg
Filters are applied after resize operations. The order of parameters does not affect the processing order.