wordpress从顶部开始裁剪图片的方法

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生成另外一张图片进行保存，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，这样的缩略图完全失去了吸引读者的功效，下面我们就来解决这个问题zXm办公区 - 实用经验教程分享！

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;}zXm办公区 - 实用经验教程分享！

这种方法需要你用bt_add_image_size代替原来我们习惯的add_image_size，具体的使用方法我们就不详细解释，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。zXm办公区 - 实用经验教程分享！

而实际上，更为简洁的方法是，我找到一个插件，似乎可以实现这个功能，你不妨下载尝试。zXm办公区 - 实用经验教程分享！

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：zXm办公区 - 实用经验教程分享！

复制代码代码如下:$s_x = floor( ($orig_w - $crop_w) / 2 );$s_y = floor( ($orig_h - $crop_h) / 2 );zXm办公区 - 实用经验教程分享！

把其中的$s_y修改为：zXm办公区 - 实用经验教程分享！

复制代码代码如下:$s_y = 0;// 或者你想要的值zXm办公区 - 实用经验教程分享！

总之，这种方法直接有效且最容易令人理解，因为$s_x和$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。zXm办公区 - 实用经验教程分享！

在stackexchange社区还有人用这样的方法更加便捷，或许你可以借鉴，但是否奏效还需要验证：zXm办公区 - 实用经验教程分享！

复制代码代码如下:add_filter('wp_generate_attachment_metadata', 'custom_crop');/function custom_crop($metadata) {/ $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/ return $metadata;}zXm办公区 - 实用经验教程分享！

以上方法由办公区教程网编辑摘抄整理自互联网可供大家参考！zXm办公区 - 实用经验教程分享！