Blur & Sharpen
Blur
-/blur/
-/blur/:strength/
Blurs images by the :strength factor. The filtering mode is Gaussian Blur,
where :strength parameter sets the blur radius — effect intensity. Technically,
:strength controls the Gaussian Blur standard deviation multiplied by ten.
The value of :strength might come up to 5000, while the default value is 10.
Note, different :strength values do not affect the operation performance.
Original image. 17Kb | /blur/20/ 10Kb | /blur/100/ 6Kb |
Blur region
-/blur_region/:two_dimensions/:two_coords/
-/blur_region/:two_dimensions/:two_coords/:strength/
Blurs the specified region of the image by the :strength factor. The filtering mode is Gaussian Blur,
where :strength parameter sets the blur radius — effect intensity. Technically,
:strength controls the Gaussian Blur standard deviation multiplied by ten.
The value of :strength might come up to 5000, while the default value is determined
automatically based on the size of the region.
Note, larger :strength values do not affect the operation performance.
Original image. | /blur_region/130x180/220,25/ | /blur_region/30%x80%/50%,10%/20/ |
Blur faces
-/blur_region/faces/
-/blur_region/faces/:strength/
When faces is specified the regions are selected automatically by utilizing face detection.
Original image. | /blur-region/faces/default strength | /blur-region/faces/250/stength 250 |
Unsharp masking
-/blur/:strength/:amount/
There is no specific operation for unsharp masking. Instead, you can adjust the
:amount of the blur applied. :amount can be set in the range from –200 to
100 and defaults to 100.
Where the :amount of:
- 100 stands for the opaque blur image.
- 0 stands for no changes in the image, the output is equal to the original.
- Any negative number would mean subtracting the difference between the blurred and original images from the original. That is the unsharp masking behavior.
You can implement unsharp masking with a large blur :strength (100;300) and a
small negative :amount (–50;–10) to increase local contrast. Fine-tuned local
contrast gives a “pop” to an image and mimics the look created by camera
lenses. Local contrast enhancements let you minimize the effects of haze, lens
flare, and “dull look.”
When implemented with a small :strength, unsharp masking increases image
sharpness. For instance, the /blur/10/-200/ transformation is the full
equivalent of /sharp/20/ with the exception that sharp
operates much faster.
You can combine unsharp masking with the sharp operation
to increase both local contrast and sharpness.
Original image. 16Kb | /blur/100/-50/ 19Kb | /blur/100/-120/ 22Kb |
/sharp/20/ 20Kb | /blur/10/-200/ 20Kb | /sharp/10/-/blur/90/-50/ 21Kb |
Sharpen
-/sharp/
-/sharp/:strength/
Sharpens an image, might be especially useful with images that were subjected to
downscaling. :strength can be in the range from 0 to 20 and defaults to the
value of 5.
Downscaled image. 15Kb | /sharp/10/ 17Kb | /sharp/20/ 19Kb |