Unwanted dashed black border when rotating image in php - php

Question

I am getting unwanted dashed black border when I rotate an image. I have tried to remove that but I am not finding any success. I am using the following function for image rotation. I try to preserve transparency. I have provided a image as well.
Here is an Image URL: http://s23.postimg.org/hep2pkol7/border.png
function imageRotation ($source, $rotang)
{
imagealphablending($source, false);
imagesavealpha($source, true);
$rotation = imagerotate($source, $rotang, imageColorAllocateAlpha($source, 0, 0, 0, 127));
imagealphablending($rotation, false);
imagesavealpha($rotation, true);
return $rotation;
}
I call the function something like that:
$rotatedImage = imageRotation($image, 10);
Here is the full code
<?php
// Some settings
$text = "Previously blogging";
$fontFace = 'Days.ttf';
$fontSize = 90;
$angle = 0;
$bbox = calculateTextBox($text, $fontFace, $fontSize, $angle);
$image = imagecreatetruecolor($bbox['width'], $bbox['height']);
// Define some colors
$black = imagecolorallocate($image, 0, 0, 0);
$yellow = imagecolorallocate($image, 0xFF, 0xFF, 0xFF);
//Fill the image with background color
imagefill($image, 0, 0, $yellow);
// Draw text
imagettftext($image, $fontSize, $angle, $bbox['left'], $bbox['top'], $black, $fontFace, $text);
$image = imageRotation($image, 20);
$im = imagecreatefromjpeg('weight-loss.jpg');
// Switch antialiasing on for one image
imageantialias($im, true);
$destWidth = imagesx($im);
$destHeight = imagesy($im);
$src_w = imagesx($image);
$src_h = imagesy($image);
$dst_x = ($destWidth - $src_w)/2;
$dst_y = ($destHeight - $src_h)/2;
imagecopy($im, $image, $dst_x, $dst_y, 0, 0, $src_w, $src_h);
header ('Content-Type: image/jpeg');
imagejpeg($im, null, 100);
imagedestroy($im);
imagedestroy($image);
function calculateTextBox($text,$fontFile,$fontSize,$fontAngle)
{
$rect = imagettfbbox($fontSize,$fontAngle,$fontFile,$text);
$minX = min(array($rect[0],$rect[2],$rect[4],$rect[6]));
$maxX = max(array($rect[0],$rect[2],$rect[4],$rect[6]));
$minY = min(array($rect[1],$rect[3],$rect[5],$rect[7]));
$maxY = max(array($rect[1],$rect[3],$rect[5],$rect[7]));
return array(
"left" => abs($minX),
"top" => abs($minY),
"width" => $maxX - $minX,
"height" => $maxY - $minY,
"box" => $rect
);
}
function imageRotation ($source, $rotang)
{
imagealphablending($source, false);
imagesavealpha($source, true);
$rotation = imagerotate($source, $rotang, imageColorAllocateAlpha($source, 0, 0, 0, 127), 0);
imagealphablending($rotation, false);
imagesavealpha($rotation, true);
return $rotation;
}
?>

Answer 1

This is neither a dashed border, nor a border at all actually. This happens because your images are low-resolution, what cause the the rotated borders to "break", because actual pixels don't rotate.
That's what I'm trying to explain:
A line, parallel to the "pixel construction"; one px is three dashes long:
-------------------------------------
It would look smooth.
Rotated line:
---
---
---
---
---
---
---
As you see, due to low resolution, it steps, not smoothly goes down.
If you use the higher resolution, the issue would go away. The visual effect of the "black" border appears because your white image contrasts with the other part of image.