I have the following problem.
I have a PNG file (http://meteopage.com/beta/image.png), which is already partially transparent and I would like to make the "pink" border also transparent.
I have read some of the instructions here and came up with a code, which does replace the border with transparent point, but all the rest, which was already transparent, turns into black: http://meteopage.com/beta/radar2.php
My code looks like this:
<?php
$file="image.png";
$im = imagecreatefrompng($file);
imagealphablending($im, false);
$new = imagecolorclosest($im, 255, 0, 255);
imagecolortransparent($im, $new);
imagesavealpha($im, true);
header('Content-type: image/png');
imagepng($im);
?>
I tried adding those imagesavealpha and imagealphablending commands, but still no luck, it is black as you can see in the link Ive attached. Would anyone know how to maintain the original transparency and just "add" those pink pixels to it?
Your image is palette-based, not true colour, so the calls to imagealphablending() and imagesavealpha() aren't needed.
The simplest way to do this is to replace the pink colour in the palette-index with a transparent one, like so:
$file = 'image.png';
$im = imagecreatefrompng($file);
$new = imagecolorclosest($im, 255, 0, 255);
imagecolorset($im, $new, 255, 0, 255, 127);
header('Content-type: image/png');
imagepng($im);
Note that this requires PHP >= 5.4 otherwise imagecolorset() won't accept the alpha parameter.
Related
I'm trying to create a function that receives a PNG image and returns it with inverted colors. However, I'm having trouble with the transparency/alpha channel: basically, transparent pixels are coming back as either black or white, and thus transparency is not retained.
This is an example of a source image (which will of course vary), a PNG with a transparent background:
I would like to invert those colors while preserving transparency/alpha channel, like a CTRL+I in Photoshop. I'm using GD imagefilter function with the IMG_FILTER_NEGATE parameter
With the code:
$im = imagecreatefrompng($image_file);
imagefilter($im, IMG_FILTER_NEGATE);
header('image/png');
imagepng($im,NULL,0);
But it yields:
As you can see, transparent pixels turned black.
I then tried adding the alpha channel to the function imagecreatefrompng (like this):
$im = imagecreatefrompng($image_file);
imagealphablending($im, false);
imagesavealpha($im, true);
imagefilter($im, IMG_FILTER_NEGATE);
header('image/png');
imagepng($im,NULL,0);
But now I get white instead of black:
Now the issue seems to happen after the imagefilter function is applied. For example, if I run this code:
$im = imagecreatefrompng($image_file);
imagealphablending($im, false);
imagesavealpha($im, true);
//imagefilter($im, IMG_FILTER_NEGATE);
header('image/png');
imagepng($im,NULL,0);
The output image retains its transparent background, while remaining identical to the original image.
How can I invert colors of transparent PNGs without losing the transparent background?
NOTE: this is not the same question as imagecreatefrompng() Makes a black background instead of transparent? - the inversion step is the tricky part here
Here's what worked for me, dealing with transparent background and inverting image. Note that I'm using base64.
$im = imagecreatefromstring(base64_decode(str_replace('data:image/png;base64,', '', $base64)));
$width = imagesx($im);
$height = imagesy($im);
$dest_image = imagecreatetruecolor($width, $height);
imagealphablending($dest_image, FALSE);
imagesavealpha($dest_image, TRUE);
imagefilter($im, IMG_FILTER_NEGATE);
imagecopyresampled($dest_image, $im, 0, 0, 0, 0, $width, $height, $width, $height);
//optional output back to base64 or use imagepng with destination
ob_start();
imagepng($dest_image);
$contents = ob_get_contents();
ob_end_clean();
$base64 = 'data:image/png;base64,'.base64_encode($contents);
I'm trying to make a image transparent using GD library from PHP but running following code, only a portion will be transparent.
$image = imagecreatefrompng("$second");
imagealphablending($image, false);
$col_transparent = imagecolorallocatealpha($image, 0, 0, 0, 127);
imagefill($image, 0, 0, $col_transparent); // set the transparent colour as the background.
imagecolortransparent ($image, $col_transparent); // actually make it transparent
imagesavealpha($image, TRUE);
header( 'Content-Type: image/png' );
imagepng($image);
Here you have original image: https://postimg.org/image/y68nw57z1/
Here it's the resulting image: https://postimg.org/image/o4n3t6ic7/
As you can see, exists parts from the resulting image that remain white.
How i can resolve this?
You are flood-fill replacing the white pixels of your image but that won't work on pixels that are completely enclosed by non-white pixels (as in any paint program). Instead you can modify the definition of the colour white to make it transparent:
$image = imagecreatefrompng($second);
imagetruecolortopalette($image, false, 255);
$index = imagecolorclosest($image, 255, 255, 255); // find index of white.
imagecolorset($image, $index, 0, 0, 0, 127); // replace white with transparent black.
header('Content-Type: image/png');
imagepng($image);
I'm trying to create a URL, that spits back a 1x1px png with a certain alpha value e.g. www.mysite/com/png.php?alpha=50 which will output a 1x1 png, with the background colour set to black, and having the opacity at 50%.
I've searched through lots of tutorials and posts trying to figure out how to do this, but I can't find anything that works. Is this possible to do with PHP alone?
Here's the closest I've gotten
<?php
header('Content-Type: image/png');
$im = imagecreatetruecolor(500, 300);
$red = imagecolorallocate($im, 255, 0, 0);
$black = imagecolorallocatealpha($im, 255, 255, 255, 50);
imagefilledrectangle($im, 0, 0, 500, 300, $black);
// Save the image
imagepng($im);
imagedestroy($im);
?>
However, that seems to overlay a 50% black colour on top of a white background.
Set the white to transparent, by adding these lines after $black = ...
$colourWhite = imagecolorallocate($im,255,255,255);
imagecolortransparent($im,$colourWhite);
I have a script that resizes uploaded images. It works fine for PNGs and JPGs but with GIFs it renders the transparency in the resized GIF black.
$src = imagecreatefromgif($file);
$dst = imagecreatetruecolor($newWidth, $newHeight);
imagecopyresampled($dst, $src, 0, 0, 0, 0, $newWidth, $newHeight, $width, $height);
imagegif($dst, $file);
From the manual page http://us3.php.net/manual/en/function.imagecopyresampled.php#104028
imagecolortransparent($new, imagecolorallocatealpha($new, 0, 0, 0, 127));
imagealphablending($new, false);
imagesavealpha($new, true);
is used by one poster to preserve transparency.
Here's a tip... Always check out user comments on php.net as they are generally very helpful in understanding the nuances of a function and providing tips for handling common tasks.
I'm assuming this goes to a web-page, which if it does you could just output the image tag with the correct attributes?
echo "<img src='$file' width='$newWidth' height='$newHeight' />";
You still have to set the transparency in the new image. The following is taken from the php docs:
<?php
// Create a 55x30 image
$im = imagecreatetruecolor(55, 30);
$red = imagecolorallocate($im, 255, 0, 0);
$black = imagecolorallocate($im, 0, 0, 0);
// Make the background transparent
imagecolortransparent($im, $black);
// ^^ This is the command you are missing.
// Draw a red rectangle
imagefilledrectangle($im, 4, 4, 50, 25, $red);
// Save the image
imagepng($im, './imagecolortransparent.png');
imagedestroy($im);
?>
In your case, you want to make the transparency the same color as the original transaprency - which I always made a hideous purple or something that would a) stick out like a sore thumb in my image manipulation software and secondly, have a RGB key that was almost impossible to have included in an image by mistake.
I am trying to write text onto a png, however when I do it puts a dark border around it, I am not sure why.
The original image:
The processed image:
Code:
// Load the image
$im = imagecreatefrompng("admin/public/images/map/order/wally.png");
// If there's an error, gtfo
if(!$im) {
die("");
}
$textColor = imagecolorallocate($im, 68, 68, 68);
$width = imagesx($im);
$height = imagesy($im);
$fontSize = 5;
$text = "AC";
// Calculate the left position of the text
$leftTextPos = ($width - imagefontwidth($fontSize)*strlen($text)) / 2;
// Write the string
imagestring($im, $fontSize, $leftTextPos, $height-28, $text, $textColor);
// Output the image
header('Content-type: image/png');
imagepng($im);
imagedestroy($im);
I've had this issue several times, let me find the answer...
Ok, found something:
imagesavealpha($im, true);
imagealphablending($im, true);
Write that before imagepng.
Yes, saving with alpha is important but loading it is important as well. Your PNG image might have transparency but it is good practice to account for that as well.
You'd need to create true color image, set alpha color and then draw your loaded image with text over it. So something like this:
// create true color image
$img = imagecreatetruecolor($width, $height);
$transparent_color = imagecolorallocatealpha($img, 255, 255, 255, 0);
imagealphablending($img, false);
imagefillrectangle($img, 0, 0, $width, $height, $transparent_color);
imagealphablending($img, true);
// draw previously loaded PNG image
imagecopy($img, $loaded_img, 0, 0, 0, 0, $width, $height);
// draw your text
// save the whole thing
imagesavealpha($img, true);
imagepng($img, $file);