imagecropauto()

(PHP 5 >= 5.5.0, PHP 7)

Crop an image automatically using one of the available modes

说明

imagecropauto(resource $image[,int $mode= IMG_CROP_DEFAULT[,float $threshold= .5[,int $color= -1]]]): resource

Automatically crops an image according to the given$mode.

参数

$image

由图象创建函数(例如imagecreatetruecolor())返回的图象资源。

$mode

One of the following constants:

IMG_CROP_DEFAULT Same as IMG_CROP_TRANSPARENT. Before PHP 7.4.0, the bundled libgd fell back to IMG_CROP_SIDES, if the image had no transparent color.IMG_CROP_TRANSPARENT Crops out a transparent background.IMG_CROP_BLACK Crops out a black background.IMG_CROP_WHITE Crops out a white background.IMG_CROP_SIDES Uses the 4 corners of the image to attempt to detect the background to crop.IMG_CROP_THRESHOLD Crops an image using the given$thresholdand$color.$threshold

Specifies the tolerance in percent to be used while comparing the image color and the color to crop. The method used to calculate the color difference is based on the color distance in the RGB(a)cube.

Used only in IMG_CROP_THRESHOLD mode.

Note: Before PHP 7.4.0, the bundled libgd used a somewhat different algorithm, so the same$thresholdyielded different results for system and bundled libgd.

$color

Either an RGB color value or a palette index.

Used only in IMG_CROP_THRESHOLD mode.

返回值

Returns a cropped image resource on success 或者在失败时返回FALSE. If the complete image was cropped,imagecrop() returns FALSE.

更新日志

版本	说明
7.4.0	The behavior of imagecropauto()in the bundled libgd has been synced with that of system libgd:IMG_CROP_DEFAULT no longer falls back to IMG_CROP_SIDES and threshold-cropping now uses the same algorithm as system libgd.
7.4.0	The default value of$modehas been changed to IMG_CROP_AUTO. Formerly, the default value has been-1which corresponds to IMG_CROP_DEFAULT, but passing-1is now deprecated.

范例

Proper handling of auto-cropping

As noted in the return value section,imagecropauto() returns FALSE if the whole image was cropped. In this example we have an image resource$imwhich should be automatically cropped only if there is something to crop; otherwise we want to proceed with the original image.

参见

• imagecrop()Crop an image to the given rectangle

In some cases the use of the IMG_CROP_WHITE or IMG_CROP_BLACK does not work. The function returns FALSE. It is best to use the IMG_CROP_THRESHOLD mode and specify the color in fourth argument as in the example below : 

Please see the note on ImageCrop() that describes an extraneous black line at the bottom of the cropped image.
http://php.net/manual/en/function.imagecrop.php#119537
Bug 67447 applies to ImageCropAuto(), too.
https://bugs.php.net/bug.php?id=67447

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