Saving a jpg as a transparent png with php - php

Question

I have a function created which processes images in different ways based on the parameters. I have comments in the function to explain a bit.
Everything works with exception to when I take a jpg image and save it as a png. I just checked, even if I use imagepng() but save it with the extension .jpg, the image displays while properly resized, but with a .jpg extension. However, if I upload the same .jpg image, use imagepng() and save it with a .png extension, I get an image of the expected width and height after the resize, in a png format, with a .png extension. While the whole image is 100% transparent I have a 1px by 1px black pixel in the top left corner.
I would appreciate it if anyone can look at this and see if they see something I am missing. I believe the 1px X 1px is coming from the point I use for the imagefill(), but I don't understand why; it should be filling all transparent as with the rest of the image.
Here is my function:
if(!function_exists("upload")){
//$image = $image file name
//$width = intended width of resized image, if 0 it will proportion to height, overrides proportion
//$height = intended width of resized image, if 0 it will proportion to width, overrides proportion
//$proportion = 2,1,0;
//------ 2 = Preserve proportions while adding a border to fill width and height
//------ 1 = retain proportion to fit within both given width and height
//------ 0 = disregard proportions and resize to the exact width and height
function upload($image, $width, $height, $proportion){
// IS GD HERE?
$gdv = get_gd_info();
if (!$gdv){
return FALSE;
}
// GET AN IMAGE THING
$ext = trim(strtolower(end(explode('.', $image))));
list($imageX, $imageY, $type) = getimagesize($image); //gets information about new server image
// GET THE LESSER OF THE RATIO OF THUMBNAIL H OR W DIMENSIONS
$ratio_w = ($width / $imageX);
$ratio_h = ($height / $imageY);
$ratio = ($ratio_w < $ratio_h) ? $ratio_w : $ratio_h;
if($width == 0){
if($imageY > $height){
$newHeight = $height;
$newWidth = ($height/$imageY) * $imageX;
}else{
$newHeight = $imageY;
$newWidth = $imageX;
}
$width = $newWidth;
$height = $newHeight;
// COMPUTE THUMBNAIL IMAGE CENTERING OFFSETS
$fromMidX = 0;
$fromMidY = 0;
}elseif($height == 0){
if ($imageX > $width){
$newWidth = $width;
$newHeight = ($width/$imageX) * $imageY;
}else{
$newHeight = $imageY;
$newWidth = $imageX;
}
$width = $newWidth;
$height = $newHeight;
// COMPUTE THUMBNAIL IMAGE CENTERING OFFSETS
$fromMidX = 0;
$fromMidY = 0;
}elseif($proportion == 2){
// COMPUTE THUMBNAIL IMAGE DIMENSIONS
$newWidth = $imageX * $ratio;
$newHeight = $imageY * $ratio;
// COMPUTE THUMBNAIL IMAGE CENTERING OFFSETS
$fromMidX = ($width - $newWidth) / 2.0;
$fromMidY = ($height - $newHeight) / 2.0;
}elseif($proportion == 1){
if ($imageX > $width){
$newHeight = ($width/$imageX) * $imageY;
$newWidth = $width;
}
if ($imageY > $height){
$newHeight = $height;
$newWidth = ($height/$imageY) * $imageX;
}
$fromMidY = 0;
$fromMidX = 0;
}elseif($proportion == 0){
$newWidth = $width;
$newHeight = $height;
$fromMidY = 0;
$fromMidX = 0;
}
switch(strtoupper($ext))
{
case 'JPG' :
case 'JPEG' :
$source = imagecreatefromjpeg($image);
break;
case 'PNG' :
$source = imagecreatefrompng($image);
break;
default : die("UNKNOWN IMAGE TYPE: $image");
}
// WHICH FUNCTIONS CAN RESIZE / RESAMPLE THE IMAGE?
if ($gdv >= 2)
{
// IF GD IS AT LEVEL 2 OR ABOVE
$target = imagecreatetruecolor($width, $height);
$color = imagecolorallocatealpha($target, 0, 0, 0, 127);
imagefill($target, 0, 0, $color);
imagesavealpha($target, TRUE);
imagecopyresampled ($target, $source, $fromMidX, $fromMidY, 0, 0, $newWidth, $newHeight, $imageX, $imageY);
}
else
{
// IF GD IS AT A LOWER REVISION LEVEL
$target = imagecreate($width, $height);
imagesavealpha($target, TRUE);
$empty = imagecolorallocatealpha($thumb,0x00,0x00,0x00,127);
imagefill($target, 0, 0, $empty);
imagecopyresized($target, $source, $fromMidX, $fromMidY, 0, 0, $newWidth, $newHeight, $imageX, $imageY);
}
// SHARPEN THE PIC
$sharpenMatrix = array
( array( -1.2, -1, -1.2 )
, array( -1, 20, -1 )
, array( -1.2, -1, -1.2 )
)
;
$divisor = array_sum(array_map('array_sum', $sharpenMatrix));
$offset = 0;
imageconvolution($target, $sharpenMatrix, $divisor, $offset);
if(imagepng($target, $image,9)){
imagedestroy($target);
}else{
}
return $image;
}
}
EDIT 1: I guess I should have noted that I am uploading a .jpg image (Ex: 100px X 200px) and converting them to .png (Ex: 400px X 200px) but am retaining the proportions of the image to fit perfectly in the center of the destination .png. So I would have a 400px X 200px .png with my image in the center and 100px on the left and right which should be transparent. This way it fits nicely in a slider without a solid color as a fill. So an example of my call to my function would be upload($image, 400, 200, 2).

Answer 1

I figured out what the issue was. The portion of code which decides whether I should use imagecreatefromjpeg or imagecreatefrompng was incorrectly going off of the extension of the passed image and NOT by its mime type. I switched it to this:
switch($type)
{
case '2' :
$source = imagecreatefromjpeg($image);
break;
case '3' :
$source = imagecreatefrompng($image);
break;
default : die("UNKNOWN IMAGE TYPE: $image");
}
where $type is coming from the line I had in there
list($imageX, $imageY, $type) = getimagesize($image);
So all together the function is:
if(!function_exists("upload")){
//$image = $image file name
//$width = intended width of resized image, if 0 it will proportion to height, overrides proportion
//$height = intended width of resized image, if 0 it will proportion to width, overrides proportion
//$proportion = 2,1,0;
//------ 2 = Preserve proportions while adding a border to fill width and height
//------ 1 = retain proportion to fit within both given width and height
//------ 0 = disregard proportions and resize to the exact width and height
function upload($image, $width, $height, $proportion){
// IS GD HERE?
$gdv = get_gd_info();
if (!$gdv){
return FALSE;
}
// GET AN IMAGE THING
$ext = trim(strtolower(end(explode('.', $image))));
list($imageX, $imageY, $type) = getimagesize($image); //gets information about new server image
// GET THE LESSER OF THE RATIO OF THUMBNAIL H OR W DIMENSIONS
$ratio_w = ($width / $imageX);
$ratio_h = ($height / $imageY);
$ratio = ($ratio_w < $ratio_h) ? $ratio_w : $ratio_h;
if($width == 0){
if($imageY > $height){
$newHeight = $height;
$newWidth = ($height/$imageY) * $imageX;
}else{
$newHeight = $imageY;
$newWidth = $imageX;
}
$width = $newWidth;
$height = $newHeight;
// COMPUTE THUMBNAIL IMAGE CENTERING OFFSETS
$fromMidX = 0;
$fromMidY = 0;
}elseif($height == 0){
if ($imageX > $width){
$newWidth = $width;
$newHeight = ($width/$imageX) * $imageY;
}else{
$newHeight = $imageY;
$newWidth = $imageX;
}
$width = $newWidth;
$height = $newHeight;
// COMPUTE THUMBNAIL IMAGE CENTERING OFFSETS
$fromMidX = 0;
$fromMidY = 0;
}elseif($proportion == 2){
// COMPUTE THUMBNAIL IMAGE DIMENSIONS
$newWidth = $imageX * $ratio;
$newHeight = $imageY * $ratio;
// COMPUTE THUMBNAIL IMAGE CENTERING OFFSETS
$fromMidX = ($width - $newWidth) / 2.0;
$fromMidY = ($height - $newHeight) / 2.0;
}elseif($proportion == 1){
if ($imageX > $width){
$newHeight = ($width/$imageX) * $imageY;
$newWidth = $width;
}
if ($imageY > $height){
$newHeight = $height;
$newWidth = ($height/$imageY) * $imageX;
}
$fromMidY = 0;
$fromMidX = 0;
}elseif($proportion == 0){
$newWidth = $width;
$newHeight = $height;
$fromMidY = 0;
$fromMidX = 0;
}
switch($type)
{
case '2' :
$source = imagecreatefromjpeg($image);
break;
case '3' :
$source = imagecreatefrompng($image);
break;
default : die("UNKNOWN IMAGE TYPE: $image");
}
// WHICH FUNCTIONS CAN RESIZE / RESAMPLE THE IMAGE?
if ($gdv >= 2)
{
// IF GD IS AT LEVEL 2 OR ABOVE
$target = imagecreatetruecolor($width, $height);
$color = imagecolorallocatealpha($target, 0, 0, 0, 127);
imagefill($target, 0, 0, $color);
imagesavealpha($target, TRUE);
imagecopyresampled ($target, $source, $fromMidX, $fromMidY, 0, 0, $newWidth, $newHeight, $imageX, $imageY);
}
else
{
// IF GD IS AT A LOWER REVISION LEVEL
$target = imagecreate($width, $height);
imagesavealpha($target, TRUE);
$empty = imagecolorallocatealpha($thumb,0x00,0x00,0x00,127);
imagefill($target, 0, 0, $empty);
imagecopyresized($target, $source, $fromMidX, $fromMidY, 0, 0, $newWidth, $newHeight, $imageX, $imageY);
}
// SHARPEN THE PIC
$sharpenMatrix = array
( array( -1.2, -1, -1.2 )
, array( -1, 20, -1 )
, array( -1.2, -1, -1.2 )
)
;
$divisor = array_sum(array_map('array_sum', $sharpenMatrix));
$offset = 0;
imageconvolution($target, $sharpenMatrix, $divisor, $offset);
if(imagepng($target, $image,9)){
imagedestroy($target);
}
return $image;
}
}
And an example call would be: upload("path/to/image/on/server.png", 400, 200, 2)
Where the image path can be either in a jpg or png mime type. But the extension MUST be .png. I suppose I can make it smarter where you can have any extension, but with the current code which uses this function it makes more sense for me to leave it as is. I would like to eventually add the option to turn on or off the transparency and instead use a solid color such as black if it is needed. Feel free to use and modify this.
There are nice hex2rgb/rgb2hex functions which I plan on using for this here