Use PHP to create thumbnails. (Cropped to square)

问题

I have a php script im currently using that creates thumbnails based on a max width and height. However, I'd like it to always create square images and crop the images when needed.

Here is what I'm using now:

    function makeThumb( $filename, $type ) {
  global $max_width, $max_height;
  if ( $type == 'jpg' ) {
   $src = imagecreatefromjpeg("blocks/img/gallery/" . $filename);
  } else if ( $type == 'png' ) {
   $src = imagecreatefrompng("blocks/img/gallery/" . $filename);
  } else if ( $type == 'gif' ) {
   $src = imagecreatefromgif("blocks/img/gallery/" . $filename);
  }
  if ( ($oldW = imagesx($src)) < ($oldH = imagesy($src)) ) {
   $newW = $oldW * ($max_width / $oldH);
   $newH = $max_height;
  } else {
   $newW = $max_width;
   $newH = $oldH * ($max_height / $oldW);
  }
  $new = imagecreatetruecolor($newW, $newH);
  imagecopyresampled($new, $src, 0, 0, 0, 0, $newW, $newH, $oldW, $oldH);
  if ( $type == 'jpg' ) {
   imagejpeg($new, 'blocks/img/gallery/thumbs/'.$filename);
  } else if ( $type == 'png' ) {
   imagepng($new, 'blocks/img/gallery/thumbs/'.$filename);
  } else if ( $type == 'gif' ) {
   imagegif($new, 'blocks/img/gallery/thumbs/'.$filename);
  }
  imagedestroy($new);
  imagedestroy($src);
 }

How would I alter this to accomplish what I want (Square thumbs)?

Thanks in advance.

回答1:

function makeThumb( $filename , $thumbSize=100 ){
  global $max_width, $max_height;
 /* Set Filenames */
  $srcFile = 'blocks/img/gallery/'.$filename;
  $thumbFile = 'blocks/img/gallery/thumbs/'.$filename;
 /* Determine the File Type */
  $type = substr( $filename , strrpos( $filename , '.' )+1 );
 /* Create the Source Image */
  switch( $type ){
    case 'jpg' : case 'jpeg' :
      $src = imagecreatefromjpeg( $srcFile ); break;
    case 'png' :
      $src = imagecreatefrompng( $srcFile ); break;
    case 'gif' :
      $src = imagecreatefromgif( $srcFile ); break;
  }
 /* Determine the Image Dimensions */
  $oldW = imagesx( $src );
  $oldH = imagesy( $src );
 /* Calculate the New Image Dimensions */
  if( $oldH > $oldW ){
   /* Portrait */
    $newW = $thumbSize;
    $newH = $oldH * ( $thumbSize / $newW );
  }else{
   /* Landscape */
    $newH = $thumbSize;
    $newW = $oldW * ( $thumbSize / $newH );
  }
 /* Create the New Image */
  $new = imagecreatetruecolor( $thumbSize , $thumbSize );
 /* Transcribe the Source Image into the New (Square) Image */
  imagecopyresampled( $new , $src , 0 , 0 , ( $newW-$thumbSize )/2 , ( $newH-$thumbSize )/2 , $thumbSize , $thumbSize , $oldW , $oldH );
  switch( $type ){
    case 'jpg' : case 'jpeg' :
      $src = imagejpeg( $new , $thumbFile ); break;
    case 'png' :
      $src = imagepng( $new , $thumbFile ); break;
    case 'gif' :
      $src = imagegif( $new , $thumbFile ); break;
  }
  imagedestroy( $new );
  imagedestroy( $src );
}

回答2:

   /* Calculate the New Image Dimensions */
   $limiting_dim = 0;
    if( $oldH > $oldW ){
     /* Portrait */
      $limiting_dim = $oldW;
    }else{
     /* Landscape */
      $limiting_dim = $oldH;
    }
   /* Create the New Image */
    $new = imagecreatetruecolor( $thumbSize , $thumbSize );
   /* Transcribe the Source Image into the New (Square) Image */
    imagecopyresampled( $new , $src , 0 , 0 , ($oldW-$limiting_dim )/2 , ( $oldH-$limiting_dim )/2 , $thumbSize , $thumbSize , $limiting_dim , $limiting_dim );

I don't have enough karma to comment on the accepted answer (Lucanos') but I found that the answer above gave black bars on the side of the thumbnail.

This code snippet (combined with the accepted answer) should copy the relevant sections of the src image without going out of bounds and producing black bars. The thumbnail is still square as per the original question.

回答3:

You want to work out an offset rather than a new width/height so that the new sample stays in proportion, then use the offset when generating the new image and give it a fixed width/height so that it'll crop to a square. A quick example that would make a 100x100 thumb (note: untested),

// Get dimensions of the src image.
list($oldW, $oldH) = getimagesize($filename);

// Work out what offset to use
if ($oldH < $oldW) 
{
    $offH = 0;
    $offW = ($oldW-$oldH)/2;
    $oldW = $oldH;
} 
elseif ($oldH > $oldW) 
{
    $offW = 0;
    $offH = ($oldH-$oldW)/2;
    $oldH = $oldW;
} 
else 
{
    $offW = 0;
    $offH = 0;
}                

// Resample the image into the new dimensions.
$new = imagecreatetruecolor(100, 100);
imagecopyresampled($new, $src, 0, 0, $offW, $offH, 100, 100, $oldW, $oldH);

回答4:

This modified function worked great for me

public function igImagePrepare($img,$name){
    $dir = 'my-images/';
    $img_name = $name.'-'.uniqid().'.jpg';

    //Your Image
    $imgSrc = $img;

    //getting the image dimensions
    list($width, $height) = getimagesize($imgSrc);

    //saving the image into memory (for manipulation with GD Library)
    $myImage = imagecreatefromjpeg($imgSrc);

    $square_size = 400;

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


                //set dimensions
                if($width> $height) {
                        $width_t=$square_size;
                        //respect the ratio
                        $height_t=round($height/$width*$square_size);
                        //set the offset
                        $off_y=ceil(($width_t-$height_t)/2);
                        $off_x=0;
                } elseif($height> $width) {
                        $height_t=$square_size;
                        $width_t=round($width/$height*$square_size);
                        $off_x=ceil(($height_t-$width_t)/2);
                        $off_y=0;
                }
                else {
                        $width_t=$height_t=$square_size;
                        $off_x=$off_y=0;
                }


   /* Create the New Image */
    $new = imagecreatetruecolor( $square_size , $square_size );
   /* Transcribe the Source Image into the New (Square) Image */
    $bg = imagecolorallocate ( $new, 255, 255, 255 );
    imagefill ( $new, 0, 0, $bg );
    imagecopyresampled( $new , $myImage , $off_x, $off_y, 0, 0, $width_t, $height_t, $width, $height );

    //final output
    imagejpeg($new, $dir.$img_name);

    return $dir.$img_name;
  }

来源：https://stackoverflow.com/questions/2686000/use-php-to-create-thumbnails-cropped-to-square