Php/docs/imagick.sigmoidalcontrastimage
Imagick::sigmoidalContrastImage
(PECL imagick 2, PECL imagick 3)
Imagick::sigmoidalContrastImage — Adjusts the contrast of an image
说明
public Imagick::sigmoidalContrastImage
( bool $sharpen
, float $alpha
, float $beta
[, int $channel = Imagick::CHANNEL_DEFAULT
] ) : bool
Adjusts the contrast of an image with a non-linear sigmoidal contrast
algorithm. Increase the contrast of the image using a sigmoidal transfer
function without saturating highlights or shadows. Contrast indicates
how much to increase the contrast (0 is none; 3 is typical; 20 is
pushing it); mid-point indicates where midtones fall in the resultant
image (0 is white; 50 is middle-gray; 100 is black). Set sharpen to
true to increase the image contrast otherwise the contrast is reduced.
See also » ImageMagick v6 Examples - Image Transformations — Sigmoidal Non-linearity Contrast
参数
sharpen- If true increase the contrast, if false decrease the contrast.
alpha- The amount of contrast to apply. 1 is very little, 5 is a significant amount, 20 is extreme.
beta- Where the midpoint of the gradient will be. This value should be in the range 0 to 1 - mutliplied by the quantum value for ImageMagick.
channel- Which color channels the contrast will be applied to.
返回值
成功时返回 true。
范例
Example #1 Create a gradient image using Imagick::sigmoidalContrastImage() suitable for blending two images together smoothly, with the blending defined by $contrast and $the midpoint
<?phpfunction generateBlendImage($width, $height, $contrast = 10, $midpoint = 0.5) { $imagick = new Imagick(); $imagick->newPseudoImage($width, $height, 'gradient:black-white'); $quanta = $imagick->getQuantumRange(); $imagick->sigmoidalContrastImage(true, $contrast, $midpoint * $quanta["quantumRangeLong"]); return $imagick; }?>
错误／异常
错误时抛出 ImagickException。
