$_params
$_params : array
Valid parameters: - radius: (float) Thickness of the sharpened edge. Should be greater than sigma (or 0, and imagick will attempt to auto choose).
In general, radius should be roughly output dpi / 150. So for display purposes a radius of 0.5 is suggested.
- amount: (float) Amount of the difference between original and the blur image that gets added back to the original. Can be thought of as the "strength" of the effect. Too high may cause blocking of shadows and highlights. Given a decimal value indicating percentage, e.g. 1.2 = 120%
- threshold: (float) Determines how large the brightness delta between adjacent pixels needs to be to sharpen the edge. Larger values == less sharpening. Useful for preventing noisy images from being oversharpened.
- channel: (integer) Which channel to apply the sharpening to.