Crop an image automatically using one of the available modes

# imagecropauto

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

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

### 说明

function 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
        $im = $cropped;       // assign the cropped image to $im
    }
    ?>

### 参见

- imagecrop() - Crop an image to the given rectangle

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