imagecropauto

(PHP 5 >= 5.5.0, PHP 7, PHP 8)

imagecropauto — Crop an image automatically using one of the available modes

说明

imagecropauto(
    GdImage $image,
    int $mode = IMG_CROP_DEFAULT,
    float $threshold = 0.5,
    int $color = -1
): GdImage|false

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 GdImage 对象。

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 threshold and 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.

注意: Before PHP 7.4.0, the bundled libgd used a somewhat different algorithm, so the same threshold yielded 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 object on success 或者在失败时返回 false. false is also returned if the whole image was cropped.

更新日志

版本	说明
8.0.0	`image` 现在需要 GdImage 实例；之前需要有效的 `gd` resource。
8.0.0	On success, this function returns a GDImage instance now; previously, a resource was returned.
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 `mode` has been changed to `IMG_CROP_AUTO`. Formerly, the default value has been `-1` which corresponds to `IMG_CROP_DEFAULT`, but passing `-1` is now deprecated.

示例

示例 #1 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 object $im which should be automatically cropped only if there is something to crop; otherwise we want to proceed with the original image.

<?php
$cropped = imagecropauto($im, IMG_CROP_DEFAULT);
if ($cropped !== false) { // in case a new image object was returned
    imagedestroy($im);    // we destroy the original image
    $im = $cropped;       // and assign the cropped image to $im
}
?>

参见

imagecrop() - Crop an image to the given rectangle

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User Contributed Notes 2 notes

down

raphael.deiana ¶

8 years ago


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 :

<?php

$original_img = imagecreatefromjpeg($image_path);

// Use this :
$cropped_img_white = imagecropauto($original_img , IMG_CROP_THRESHOLD, null, 16777215);
// Rather than :
$cropped_img_white = imagecropauto($original_img , IMG_CROP_WHITE);

// AND

// Use this :
$cropped_img_black = imagecropauto($original_img , IMG_CROP_THRESHOLD, null, 0);
// Rather than :
$cropped_img_black = imagecropauto($original_img , IMG_CROP_BLACK);

?>

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pj dot mueller at protonmail dot ch ¶

2 years ago


I don’t know why you can’t set the threshold for the four sides filter (IMG_CROP_SIDES) so here’s how to do it manually using the IMG_CROP_THRESHOLD filter instead.

$threshold = .5;

$im = imagecreatefromjpeg('somefile.jpg');

$width = imagesx($im);
$height = imagesy($im);

$arr = [
    [0,0],
    [$width-1,0],
    [0,$height-1],
    [$width-1,$height-1],
];

$red = 0;
$green = 0;
$blue = 0;

// grab the colours from all four corners
foreach( $arr as $arr2 ) {
    $thisColor = imagecolorat($im, $arr2[0], $arr2[1]); 

    $rgb = imagecolorsforindex($im, $thisColor); 
    $red += round(round(($rgb['red'] / 0x33)) * 0x33); 
    $green += round(round(($rgb['green'] / 0x33)) * 0x33); 
    $blue += round(round(($rgb['blue'] / 0x33)) * 0x33); 
}

// and average them
$red /= 4;
$green /= 4;
$blue /= 4;

$newColor = imagecolorallocate($im, $red, $green, $blue);            

$cropped = imagecropauto($im, IMG_CROP_THRESHOLD, $threshold, $newColor);

imagejpg($cropped, 'somefile.cropped.jpg');

imagedestroy($im);
imagedestroy($cropped);

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