I 've got this image:
i use php5 and gd2 library to achieve a transparent background, but the result is not what i have expected(you need a dark background to see the difference):
and here is my code:
$size = getimagesize($img_url);
$img = imagecreatefrompng($img_url);
$im_tc = imagecreatetruecolor($size[0],$size[1]);
imagecopyresampled($im_tc,$img,0,0,0,0,$size[0],$size[1],$size[0],$size[1]);
imagedestroy($img);
$white = imagecolorallocatealpha($im_tc, 255, 255, 255,127);
imagecolortransparent($im_tc, $white);
imagepng($im_tc,'image.png');
Any help would be appreciated! :)
Your original image doesn't have a transparent background, but you're trying to create one by changing all pure-white pixels to transparent. As the text has a shadow/glow around it, those pixels aren't quite white, and won't become transparent. You have a couple options here:
Use an image editor (GIMP, Photoshop, etc.) and their fine-grained selection tools to perform a smart selection of the "background", then remove that. Photoshop, at least, has extremely useful options available on its magic wand tool to choose threshold, feathering, and more.
Pick more colours to make "transparent." Instead of just white, choose all of the shades of gray, minus the exact colour that ".gr" is set in. This should make all of the shadowed parts of the image transparent as well, although the edges may be less than perfect (i.e.: not feathered, slightly jagged.)
Related
I use this code to make all white pixels transparent:
$img = imagecreatefromjpeg('test.jpg');
$remove = imagecolorallocate($img, 255, 255, 255);
imagecolortransparent($img, $remove);
imagepng($img, 'bla.png');
But I also want some "almost white" pixels to be transparent like 254, 255, 255 etc. How could I add that?
If your question is how to remove a contiguous area with similar color range; I must say that it's hard using PHP's GD library. You should take a look at ImageMagick which is a much more powerful image processing library and has PHP integration.
If you choose to use ImageMagick instead, you'll have access to a lot of third-party scripts that does amazing image processings. One of which is Fred Weinhaus' MagicWand. It does what you're looking for.
You seed it with an x and y coordinate, it can extract the color of that coordinate and make it transparent with a configurable color dissimilarity threshold (fuzz factor). Have a look how it can match a gradient of blue:
I had the same problem. With a black and white image. But white was not very white. So before to set transparency, I do a filter to increase the contrast. And I have an image with real black and real white. And when I use transparency on white color, it's works fine.
Filter's example :
imagefilter($src,IMG_FILTER_CONTRAST,-50);
i am trying to to colorize a black and white picture on my server.
i have tried doing this with multiple methods and the only one that kind-of-works is gd imagefilter via filter IMG_FILTER_COLORIZE.
it does kind of colorize the image in exactly the same color that i want, but it loses all the details on the image, as if it just trimmed black dots that were not black enough and thinned all the black lines, making them almost invisible. here is what i'm talking about:
this result was achieved with this code
$im=imagecreatefromjpeg($orig_file);
imagefilter($im, IMG_FILTER_COLORIZE, 71, 92, 10);
imagejpeg($im, $output_file, 95);
why is this happening? are there any other methods how i could colorize the image? my original image is quite large and i can't iterate over it as it is too slow; that's why i'm trying to use a library that would do this
i have managed to achieve the desired result with help of Imagick and compositeImage. here is the result
how i achieved it is kind of a trick that works only in a very specific condition- which is the need to have the background white and only black/gray objects in front (or the exact opposite). this technique wouldn't work on a background with transparency
the idea is to have 2 layers- underneath is the layer with original grayscale image and the top layer- fully filled with the desired color. then you composite these images using "COMPOSITE_LIGHTEN" (you might use other methods, like darken for example- if you have white objects on a black background)
this is the code
$base_color="#475c0a";
$im=new Imagick($orig_file);
$im2 = new Imagick();
$im2->newImage($im->getImageWidth(), $im->getImageHeight(), new ImagickPixel($base_color) );
$im->compositeImage($im2, Imagick::COMPOSITE_LIGHTEN, 0, 0);
$im->writeImage($new_image_path);
hope this will help someone out
I have pieced together a PHP class to perform various image related functions using GD functions of PHP.
It works great for all image types. Rotate, flip, resize, crop and to a lesser extent, watermark.
All but the latter work perfectly. For example after a few changes, rotated PNG images retained their transparency whereas before they were losing that and the background turning black. Common problem, it appears. But all working now.
Where I'm still getting stuck is watermarking a PNG image with another PNG image. It appears to work fine with JPG and other images. This is the code (simplified):
public function writeWatermarkSimple()
{
$watermarkFile = 'watermark.png';
$watermarkImage = imagecreatefrompng($watermarkFile);
imagealphablending($watermarkImage, false);
imagesavealpha($watermarkImage, true);
$imageFile = 'image.png';
$baseImage = imagecreatefrompng($imageFile);
imagealphablending($baseImage, false);
imagesavealpha($baseImage, true);
$marginH = imagesx($baseImage) - imagesx($watermarkImage);
$marginV = imagesy($baseImage) - imagesy($watermarkImage);
$cut = imagecreatetruecolor(imagesx($watermarkImage), imagesy($watermarkImage));
imagecopy($cut, $baseImage, 0, 0, $marginH, $marginV, imagesx($watermarkImage), imagesy($watermarkImage));
imagecopy($cut, $watermarkImage, 0, 0, 0, 0, imagesx($watermarkImage), imagesy($watermarkImage));
imagecopymerge($baseImage, $cut, $marginH, $marginV, 0, 0, imagesx($watermarkImage), imagesy($watermarkImage), 80);
if (!imagepng($baseImage, 'watermarked_image.png'))
{
return false;
}
return true;
}
This has been pieced together with various guides and advice people have given based on a similar issue. Again, working perfectly with JPG images and PNG watermarks, but not PNG & PNG.
Some example images:
http://i.imgur.com/hHRWinj.png - This is the watermark I'm using.
http://i.imgur.com/6sy8Ncs.png - This is the image I'm applying the watermark to.
http://i.imgur.com/ghovYLm.png - This is the end result.
The bit I find interesting is that any part of the watermark that is overlaid on a non-transparent portion of the image is working fine. Just the rest of it has the black background.
This leads me to believe I'm close, and I hope that the expertise of you fine people may lead me to the solution.
Thanks ever so for reading.
So, I'm not giving up on finding the correct answer to do this using GD. However, I was overjoyed to find that what needed up to 30 lines of code with GD can be achieved using much less with ImageMagick:
$image = new Imagick();
$image->readimage($this->_image);
$watermark = new Imagick();
$watermark->readimage($this->_watermark->_getImage());
$watermark->evaluateImage(Imagick::EVALUATE_DIVIDE, 2, Imagick::CHANNEL_ALPHA);
$image->compositeImage($watermark, imagick::COMPOSITE_OVER, $marginH, $marginV);
So this is before (with GD):
http://i.imgur.com/AlS0TcO.png
And after (with ImageMagick and the code above):
http://i.imgur.com/zBxlC3R.png
If anyone has an answer that is purely GD then I'd be immensely grateful.
Ran into some similar issues recently and while this may not exactly solve your problem, these were some useful discoveries that I made.
In my case, I have an original .jpg image and a watermark .png image. The watermark image has a fully transparent background. I wanted to specify the opacity in my script and have it change the watermark opacity before placing it on top of the origina image. Most posts out there regarding PHP watermarking assume that the original watermark .png file already has the solid watermark portion set to the correct opacity rather than changing it via the script.
gd didn't like a 24 bit .png and caused some goofy issues. Switching to 8 bit resolved that with gd. On the other hand, imagick works very well with a 24 bit .png and the final result seems to be better.
For me, using gd worked just fine if I was opening the original watermark .png and using imagecopymerge() to set the watermark transparency. If however I tried to scale the original watermark .png (which has transparent background) first, then I would get similar results as you with black or white background portion of where watermark image is. See How do I resize pngs with transparency in PHP? for a partial solution by filling the new wm image with transparent rectangle first. For me this still produced an opaque white background on the final result no matter what I tried.
I switched to imagick and was using setImageOpacity() to change the transparency of my watermark .png before applying it on top of my original image and I was still getting the same effect with a black background. Finally read in the PHP doc for setImageOpacity() that if the original .png has any transparent pixels and you try to lower the opacity, those pixels become opaque (black) with the new transparency applied. Instead, need to use the evaluateImage() function. This will instead evaluate each pixel's alpha channel only and divide by the specifid number.
I assume the black / white background issue with gd is likely due to similar ways that it treats alpha channels when scaling / combining as compared to imagick and if you want to do it all in gd you just need to find some similar way to evaluate and manipulate the alpha channel per-pixel because the "easy" ways seem to take an already transparent background and make it opaque.
So, the solution:
Assuming you want to apply your watermark at an opacity of 45% and you're using imagick, then instead of this:
$watermark->setImageOpacity(.45);
do this
$watermark->evaluateImage(Imagick::EVALUATE_DIVIDE, (1/.45), Imagick::CHANNEL_ALPHA);
You need to divide 1 by your opacity to get the demoninator by which the function will divide the alpha channel value for each pixel. In this case, 1/.45 = 2.2222, so then the function will divide the alpha channel of each pixel by 2.2222. This means a solid pixel (alpha of 1) would result in 1/2.2222 or .45 alpha or transparency when finished. Any pixels that were already transparent (alpha 0) would stay transparent because 0 divided by anything is always what? Zero!
After you change the watermark transparency then you can use compositeImage() to merge the watermark onto the original image.
I'm making a skin previewer for my site; I need to rotate parts of an image to create a representation of this for my users to see.
The skin is a PNG file, and all parts of it may have transparency or even none at all.
I need to be able to rotate this image while keeping any transparency inside the image transparent, while also having the extended borders (You know, the area that wasn't part of the image before it was rotated) transparent.
All of my attempts have left a black border around the image itself.
Any help?
Cut out the piece of the image you want to rotate
Rotate preserving alpha using something like this http://www.exorithm.com/algorithm/view/rotate_image_alpha
Merge back in preserving alpha using the following:
-
imagesetbrush($destimg, $srcimg);
// x, y are the center of target paste location
imageline($destimg, $x, $y, $x, $y, IMG_COLOR_BRUSHED);
I use that to rotate a PNG and preserve transparency color. Works like a charm. It's "basic GD".
$rotation = 135;
$handle_rotated = imagerotate($handle_not_rotated,$rotation,0);
imagealphablending($handle_rotated, true);
imagesavealpha($handle_rotated, true);
Don't know if it's what you're looking for?
You may want to check here for some uses for libpng (which will need zlib). If you are on linux you can write something in perl. CPAN GD module might be your ticket.
I'm writing code this week to dynamically change the color of images. As long as the image is square or rectangle, the code below works perfectly. However, I have an image that has rounded corners (filled with a spot color and the background outside the corners is white.)
Can someone tell me if there's a simple way to color an image that has rounded corners using the imagecolorset function (or any other php method)?
I only want the non white areas of the image to be colored (In case you're wondering, I'm disallowing the color white to be applied to the image).
Note, perhaps a better way to do this would be to use a PNG image that has transparent background (rather than my gif image). If you think that's a better approach, please advise.
Here's the function that I'm working with...
function set_theme_color_header($hex)
{
$info = hexToRGB($hex); //calls a helper function which translates the hex to RGB
$img = imagecreatefromgif('header-template.gif'); //again, this could be a PNG image, but we always start with this image, then create a color copy
$color = imagecolorallocate($img, $info["red"], $info["green"], $info["blue"]);
imagecolorset($img, 0, $info["red"], $info["green"], $info["blue"]);
imagegif($img, 'header.gif'); //only problem is that the imagecolorset function creates a messy fill at the corners
}
GD does not handle gif's very well. I recommend creating a png image with your rounded corners, then use GD's imagefilter($img, IMG_FILTER_COLORIZE, $info["red"], $info["green"], $info["blue"], $alpha) function. Then save the image as a gif.
Alternatively, use php's imagick library to literally draw the image. imagick is about a billion times better than GD. Poorly documented, but...the basic stuff isnnt too hard. See the tut link below.
Search php.net for "imagick" to see all the functions.
imagick tutorial
i really do not not why you are doing this, but maybe have a look at phpTumb (and its demos here).