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wordpress从顶部开始裁剪图片的方法

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小雨敲窗y 显示全部楼层 发表于 2021-8-15 20:23:47 |阅读模式 打印 上一主题 下一主题
wordpress默认情况下,裁剪的图片会直接裁剪图片的中间部分,例如你上传了一张美女图片,上传上去由于图片的尺寸超出了内部规定的尺寸,wordpress会对其进行裁剪,按照规定的尺寸裁剪好后天生另外一张图片进行生存,可惜的是,当你调用这张图片的时候发现,美女的头被卡擦了,如许的缩略图完全失去了吸引读者的功效,下面我们就来办理这个题目

复制代码代码如下:
<?php
/* Example Usage:
* bt_add_image_size( 'product-screenshot', 300, 300, array( 'left', 'top' ) );
* bt_add_image_size( 'product-feature', 460, 345, array( 'center', 'top' ) );
*/

add_filter( 'intermediate_image_sizes_advanced', 'bt_intermediate_image_sizes_advanced' );
add_filter( 'wp_generate_attachment_metadata', 'bt_generate_attachment_metadata', 10, 2 );

/**
* Registers a new image size with cropping positions
*
* The $crop parameter works as in the 'add_image_size' function taking true or
* false values. If set to true, the default cropping position is 'center', 'center'.
*
* The $crop parameter also takes an array of the format
* array( x_crop_position, y_crop_position )
* x_crop_position can be 'left', 'center', 'right'
* y_crop_position can be 'top', 'center', 'bottom'
*
* @param string $name Image size identifier.
* @param int $width Image width.
* @param int $height Image height.
* @param bool|array $crop Optional, default is false. Whether to crop image to specified height and width or resize. An array can specify positioning of the crop area.
* @return bool|array False, if no image was created. Metadata array on success.
*/
function bt_add_image_size( $name, $width = 0, $height = 0, $crop = false ) {
    global $_wp_additional_image_sizes;
    $_wp_additional_image_sizes[$name] = array( 'width' => absint( $width ), 'height' => absint( $height ), 'crop' => $crop );
}


/**
* Returning no sizes (an empty array) will force
* wp_generate_attachment_metadata to skip creating intermediate image sizes on
* upload, then we can run our own resizing functions by hooking into the
* 'wp_generate_attachment_metadata' filter
*/
function bt_intermediate_image_sizes_advanced( $sizes ) {
    return array();
}


function bt_generate_attachment_metadata( $metadata, $attachment_id ) {
    $attachment = get_post( $attachment_id );
   
    $uploadPath = wp_upload_dir();
    $file = path_join($uploadPath['basedir'], $metadata['file']);

    if ( !preg_match('!^image/!', get_post_mime_type( $attachment )) || !file_is_displayable_image( $file ) ) return $metadata;

    global $_wp_additional_image_sizes;

    foreach ( get_intermediate_image_sizes() as $s ) {
        $sizes[$s] = array( 'width' => '', 'height' => '', 'crop' => FALSE );
        if ( isset( $_wp_additional_image_sizes[$s]['width'] ) )
            $sizes[$s]['width'] = intval( $_wp_additional_image_sizes[$s]['width'] ); // For theme-added sizes
        else
            $sizes[$s]['width'] = get_option( "{$s}_size_w" ); // For default sizes set in options
        if ( isset( $_wp_additional_image_sizes[$s]['height'] ) )
            $sizes[$s]['height'] = intval( $_wp_additional_image_sizes[$s]['height'] ); // For theme-added sizes
        else
            $sizes[$s]['height'] = get_option( "{$s}_size_h" ); // For default sizes set in options
        if ( isset( $_wp_additional_image_sizes[$s]['crop'] ) )
            $sizes[$s]['crop'] = $_wp_additional_image_sizes[$s]['crop'];
        else
            $sizes[$s]['crop'] = get_option( "{$s}_crop" );
    }

    foreach ( $sizes as $size => $size_data ) {
        $resized = bt_image_make_intermediate_size( $file, $size_data['width'], $size_data['height'], $size_data['crop'] );
        if ( $resized )
            $metadata['sizes'][$size] = $resized;
    }
   
    return $metadata;
}


/**
* Resize an image to make a thumbnail or intermediate size.
*
* The returned array has the file size, the image width, and image height. The
* filter 'image_make_intermediate_size' can be used to hook in and change the
* values of the returned array. The only parameter is the resized file path.
*
* @param string $file File path.
* @param int $width Image width.
* @param int $height Image height.
* @param bool|array $crop Optional, default is false. Whether to crop image to specified height and width or resize. An array can specify positioning of the crop area.
* @return bool|array False, if no image was created. Metadata array on success.
*/
function bt_image_make_intermediate_size( $file, $width, $height, $crop = false ) {
    if ( $width || $height ) {
        $resized_file = bt_image_resize( $file, $width, $height, $crop, null, null, 90 );
        if ( !is_wp_error( $resized_file ) && $resized_file && $info = getimagesize( $resized_file ) ) {
            $resized_file = apply_filters('image_make_intermediate_size', $resized_file);
            return array(
                'file' => wp_basename( $resized_file ),
                'width' => $info[0],
                'height' => $info[1],
            );
        }
    }
    return false;
}



/**
* Retrieve calculated resized dimensions for use in imagecopyresampled().
*
* Calculate dimensions and coordinates for a resized image that fits within a
* specified width and height. If $crop is true, the largest matching central
* portion of the image will be cropped out and resized to the required size.
*
* @param int $orig_w Original width.
* @param int $orig_h Original height.
* @param int $dest_w New width.
* @param int $dest_h New height.
* @param bool $crop Optional, default is false. Whether to crop image or resize.
* @return bool|array False, on failure. Returned array matches parameters for imagecopyresampled() PHP function.
*/
function bt_image_resize_dimensions($orig_w, $orig_h, $dest_w, $dest_h, $crop = false) {

    if ($orig_w <= 0 || $orig_h <= 0)
        return false;
    // at least one of dest_w or dest_h must be specific
    if ($dest_w <= 0 && $dest_h <= 0)
        return false;

    if ( $crop ) {
        // crop the largest possible portion of the original image that we can size to $dest_w x $dest_h
        $aspect_ratio = $orig_w / $orig_h;
        $new_w = min($dest_w, $orig_w);
        $new_h = min($dest_h, $orig_h);

        if ( !$new_w ) {
            $new_w = intval($new_h * $aspect_ratio);
        }

        if ( !$new_h ) {
            $new_h = intval($new_w / $aspect_ratio);
        }

        $size_ratio = max($new_w / $orig_w, $new_h / $orig_h);

        $crop_w = round($new_w / $size_ratio);
        $crop_h = round($new_h / $size_ratio);

        if ( !is_array( $crop ) || count( $crop ) != 2 ) {
            $crop = apply_filters( 'image_resize_crop_default', array( 'center', 'center' ) );
        }
        
        switch ( $crop[0] ) {
            case 'left': $s_x = 0; break;
            case 'right': $s_x = $orig_w - $crop_w; break;
            default: $s_x = floor( ( $orig_w - $crop_w ) / 2 );
        }

        switch ( $crop[1] ) {
            case 'top': $s_y = 0; break;
            case 'bottom': $s_y = $orig_h - $crop_h; break;
            default: $s_y = floor( ( $orig_h - $crop_h ) / 2 );
        }
    } else {
        // don't crop, just resize using $dest_w x $dest_h as a maximum bounding box
        $crop_w = $orig_w;
        $crop_h = $orig_h;

        $s_x = 0;
        $s_y = 0;

        list( $new_w, $new_h ) = wp_constrain_dimensions( $orig_w, $orig_h, $dest_w, $dest_h );
    }

    // if the resulting image would be the same size or larger we don't want to resize it
    if ( $new_w >= $orig_w && $new_h >= $orig_h )
        return false;

    // the return array matches the parameters to imagecopyresampled()
    // int dst_x, int dst_y, int src_x, int src_y, int dst_w, int dst_h, int src_w, int src_h
    return array( 0, 0, (int) $s_x, (int) $s_y, (int) $new_w, (int) $new_h, (int) $crop_w, (int) $crop_h );

}


/**
* Scale down an image to fit a particular size and save a new copy of the image.
*
* The PNG transparency will be preserved using the function, as well as the
* image type. If the file going in is PNG, then the resized image is going to
* be PNG. The only supported image types are PNG, GIF, and JPEG.
*
* Some functionality requires API to exist, so some PHP version may lose out
* support. This is not the fault of WordPress (where functionality is
* downgraded, not actual defects), but of your PHP version.
*
* @since 2.5.0
*
* @param string $file Image file path.
* @param int $max_w Maximum width to resize to.
* @param int $max_h Maximum height to resize to.
* @param bool $crop Optional. Whether to crop image or resize.
* @param string $suffix Optional. File Suffix.
* @param string $dest_path Optional. New image file path.
* @param int $jpeg_quality Optional, default is 90. Image quality percentage.
* @return mixed WP_Error on failure. String with new destination path.
*/
function bt_image_resize( $file, $max_w, $max_h, $crop = false, $suffix = null, $dest_path = null, $jpeg_quality = 90 ) {

    $image = wp_load_image( $file );
    if ( !is_resource( $image ) )
        return new WP_Error( 'error_loading_image', $image, $file );

    $size = @getimagesize( $file );
    if ( !$size )
        return new WP_Error('invalid_image', __('Could not read image size'), $file);
    list($orig_w, $orig_h, $orig_type) = $size;

    // Rotate if EXIF 'Orientation' is set
    // This code is from the reverted patch at
    // <a href="http://core.trac.wordpress.org/changeset/11746/trunk/wp-includes/media.php">http://core.trac.wordpress.org/changeset/11746/trunk/wp-includes/media.php</a>
    $rotate = false;
    if ( is_callable( 'exif_read_data' ) && in_array( $orig_type, apply_filters( 'wp_read_image_metadata_types', array( IMAGETYPE_JPEG, IMAGETYPE_TIFF_II, IMAGETYPE_TIFF_MM ) ) ) ) {
        $exif = @exif_read_data( $file, null, true );
        if ( $exif && isset( $exif['IFD0'] ) && is_array( $exif['IFD0'] ) && isset( $exif['IFD0']['Orientation'] ) ) {
            if ( 6 == $exif['IFD0']['Orientation'] )
                $rotate = 90;
            elseif ( 8 == $exif['IFD0']['Orientation'] )
                $rotate = 270;
        }
    }
   
    if ( $rotate )
        list($max_h,$max_w) = array($max_w,$max_h);

    $dims = bt_image_resize_dimensions($orig_w, $orig_h, $max_w, $max_h, $crop);
    if ( !$dims )
        return new WP_Error( 'error_getting_dimensions', __('Could not calculate resized image dimensions') );
    list($dst_x, $dst_y, $src_x, $src_y, $dst_w, $dst_h, $src_w, $src_h) = $dims;

    $newimage = wp_imagecreatetruecolor( $dst_w, $dst_h );

    if ( $rotate )
        list($src_y,$src_x) = array($src_x,$src_y);

    imagecopyresampled( $newimage, $image, $dst_x, $dst_y, $src_x, $src_y, $dst_w, $dst_h, $src_w, $src_h);

    // convert from full colors to index colors, like original PNG.
    if ( IMAGETYPE_PNG == $orig_type && function_exists('imageistruecolor') && !imageistruecolor( $image ) )
        imagetruecolortopalette( $newimage, false, imagecolorstotal( $image ) );

    // we don't need the original in memory anymore
    imagedestroy( $image );

    // $suffix will be appended to the destination filename, just before the extension
    if ( !$suffix ) {
        if ( $rotate )
            $suffix = "{$dst_h}x{$dst_w}";
        else
            $suffix = "{$dst_w}x{$dst_h}";
    }

    $info = pathinfo($file);
    $dir = $info['dirname'];
    $ext = $info['extension'];
    $name = wp_basename($file, ".$ext");

    if ( !is_null($dest_path) and $_dest_path = realpath($dest_path) )
        $dir = $_dest_path;
    $destfilename = "{$dir}/{$name}-{$suffix}.{$ext}";

    if ( IMAGETYPE_GIF == $orig_type ) {
        if ( !imagegif( $newimage, $destfilename ) )
            return new WP_Error('resize_path_invalid', __( 'Resize path invalid' ));
    } elseif ( IMAGETYPE_PNG == $orig_type ) {
        if ( !imagepng( $newimage, $destfilename ) )
            return new WP_Error('resize_path_invalid', __( 'Resize path invalid' ));
    } else {
        if ( $rotate ) {
            $newimage = _rotate_image_resource( $newimage, 360 - $rotate );
        }
        
        // all other formats are converted to jpg
        $destfilename = "{$dir}/{$name}-{$suffix}.jpg";
        $return = imagejpeg( $newimage, $destfilename, apply_filters( 'jpeg_quality', $jpeg_quality, 'image_resize' ) );
        if ( !$return )
            return new WP_Error('resize_path_invalid', __( 'Resize path invalid' ));
    }

    imagedestroy( $newimage );

    // Set correct file permissions
    $stat = stat( dirname( $destfilename ));
    $perms = $stat['mode'] & 0000666; //same permissions as parent folder, strip off the executable bits
    @ chmod( $destfilename, $perms );

    return $destfilename;
}

这种方法必要你用bt_add_image_size取代原来我们风俗的add_image_size,具体的使用方法我们就不具体解释,总之这个函数给出了第三个参数,让你可以规定裁剪的开始位置。
而实际上,更为简便的方法是,我找到一个插件,似乎可以实现这个功能,你不妨下载实验。
Shailan.com Staff则提供了一个更直接的方法,就是修改wordpress系统文件/wp-includes/media.php,找到:

复制代码代码如下:
$s_x = floor( ($orig_w - $crop_w) / 2 );
$s_y = floor( ($orig_h - $crop_h) / 2 );

把此中的$s_y修改为:

复制代码代码如下:
$s_y = 0;// 或者你想要的值

总之,这种方法直接有用且最轻易令人理解,由于$s_x和$s_y就是wordpress系统在裁剪时,裁剪区域的起始位置。而且他还推荐了一个插件:Regenerate Thumbnails,应是基于这种方法来实现的。
在stackexchange社区还有人用如许的方法更加便捷,或许你可以鉴戒,但是否见效还必要验证:

复制代码代码如下:
add_filter('wp_generate_attachment_metadata', 'custom_crop');</p><p>function custom_crop($metadata) {</p><p>    $uploads = wp_upload_dir();
    $file = path_join( $uploads['basedir'], $metadata['file'] ); // original image file
    list( $year, $month ) = explode( '/', $metadata['file'] );
    $target = path_join( $uploads['basedir'], "{$year}/{$month}/".$metadata['sizes']['medium']['file'] ); // intermediate size file
    $image = imagecreatefromjpeg($file); // original image resource
    $image_target = wp_imagecreatetruecolor( 44, 44 ); // blank image to fill
    imagecopyresampled($image_target, $image, 0, 0, 25, 15, 44, 44, 170, 170); // crop original
    imagejpeg($image_target, $target, apply_filters( 'jpeg_quality', 90, 'image_resize' )); // write cropped to file</p><p>    return $metadata;
}

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