/*一个简单的函数来计算“精确”边界框(单像素精度)。
该函数返回具有以下键的关联数组:
left, top:您将传递给imagettftext的坐标
width, height:创建的图像尺寸*/
function calculateTextBox($font_size, $font_angle, $font_file, $text) {
$box = imagettfbbox($font_size, $font_angle, $font_file, $text);
if( !$box )
return false;
$min_x = min( array($box[0], $box[2], $box[4], $box[6]) );
$max_x = max( array($box[0], $box[2], $box[4], $box[6]) );
$min_y = min( array($box[1], $box[3], $box[5], $box[7]) );
$max_y = max( array($box[1], $box[3], $box[5], $box[7]) );
$width = ( $max_x - $min_x );
$height = ( $max_y - $min_y );
$left = abs( $min_x ) + $width;
$top = abs( $min_y ) + $height;
// to calculate the exact bounding box i write the text in a large image
$img = @imagecreatetruecolor( $width << 2, $height << 2 );
$white = imagecolorallocate( $img, 255, 255, 255 );
$black = imagecolorallocate( $img, 0, 0, 0 );
imagefilledrectangle($img, 0, 0, imagesx($img), imagesy($img), $black);
// for sure the text is completely in the image!
imagettftext( $img, $font_size,
$font_angle, $left, $top,
$white, $font_file, $text);
// start scanning (0=> black => empty)
$rleft = $w4 = $width<<2;
$rright = 0;
$rbottom = 0;
$rtop = $h4 = $height<<2;
for( $x = 0; $x < $w4; $x++ )
for( $y = 0; $y < $h4; $y++ )
if( imagecolorat( $img, $x, $y ) ){
$rleft = min( $rleft, $x );
$rright = max( $rright, $x );
$rtop = min( $rtop, $y );
$rbottom = max( $rbottom, $y );
}
// destroy img and serve the result
imagedestroy( $img );
return array( "left" => $left - $rleft,
"top" => $top - $rtop,
"width" => $rright - $rleft + 1,
"height" => $rbottom - $rtop + 1 );
}