php教程

Imagick::contrastImage

(PECL imagick 2.0.0)

Imagick::contrastImage — Change the contrast of the image

说明

Imagick::contrastImage ( bool $sharpen ) : bool

Enhances the intensity differences between the lighter and darker elements of the image. Set sharpen to a value other than 0 to increase the image contrast otherwise the contrast is reduced.

参数

sharpen

The sharpen value

返回值

成功时返回 TRUE。

错误／异常

错误时抛出 ImagickException。

范例

Example #1 Imagick::contrastImage()

<?php
function contrastImage($imagePath, $contrastType) {
    $imagick = new \Imagick(realpath($imagePath));
    if ($contrastType != 2) {
        $imagick->contrastImage($contrastType);
    }

    header("Content-Type: image/jpg");
    echo $imagick->getImageBlob();
}

?>

User Contributed Notes

removespam dot roland at tannerritchie dot com 12-Feb-2015 07:14
Both xyking and quickshiftin include errors in their comments. xyking's error is in looping through negative numbers. quickshifting is incorrect in stating that 0 *increases* contrast (it does not - it decreases it).

Here is a (tested, working) method to increment or decrement contrast:
<?php
class Images {
public function contrastImage($contrast, $imagePath){

$this->image = new Imagick();
$this->image->readImage($imagePath);                    

 if ($contrast > 0){
                for ($i = 1; $i < $contrast; $i++){
                    $this->image->contrastImage(1);
                }
            }else if ($contrast <= 0) {

                for ($i = 0; $i > $contrast; $i--) {

                    $this->image->contrastImage(0);
                }
            }
     }
}
?>
quickshiftin at gmail dot com 07-Nov-2014 09:24
xyking's comment is wrong so be careful if you read it. You pass a value of 0 to *increase* the contrast.
xyking 16-Apr-2010 08:14
Tip:
<?php
$image->contrastImage(1); //Increase contrast once
$image->contrastImage(1); //Increase contrast more
$image->contrastImage(1); //Increase contrast even more

$image->contrastImage(0); //Decrease contrast once
$image->contrastImage(0); //Decrease contrast more
$image->contrastImage(0); //Decrease contrast even more

//This could be made into a function like this:
public function contrast($level) {
        $level = (int)$level;
        if ($level < -10) {
            $level = -10;
        } else if ($level > 10) {
            $level = 10;
        }
        if ($level > 0) {
            for ($i = 0; $i < $level; $i++) {
                $this->image->contrastImage(1);
            }
        } else if ($level < 0) {
            for ($i = $level; $i > 0; $i--) {
                $this->image->contrastImage(0);
            }
        }
    }
?>

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