Related
I have the following piece of code:
define(RED_THESHOLD,100);
define(GREEN_THESHOLD,200);
define(BLUE_THESHOLD,100);
function thresholdImage(String $imgdata){
$original_limit = ini_get('memory_limit');
ini_set('memory_limit', '-1');
$imageResource = imagecreatefromstring($imgData);
// Limit red green and blue color channels here
}
But I do not know how I can apply the color the constants:
RED_THESHOLD
GREEN_THESHOLD
BLUE_THESHOLD
According to the classic algorithms I need to read pixel by pixel each channel and apply the threshold by the following piece of code (I use images red channel as an example):
$new_pixel_value = ($red_pixel_value>RED_THESHOLD)?RED_THESHOLD:$red_pixel_value;
Do you know how I can do this?
This can be done by finding the color index for each pixel, converting that into RGBA, then constraining those values, converting it back into a color index and setting the pixel.
<?php
const RED_THESHOLD = 255;
const GREEN_THESHOLD = 10;
const BLUE_THESHOLD = 10;
$image = imagecreatefrompng('test.png');
$maxX = imagesx($image);
$maxY = imagesy($image);
for ($y = 0; $y < $maxY; ++$y) {
for ($x = 0; $x < $maxX; ++$x) {
$existing = imagecolorsforindex($image, imagecolorat($image, $x, $y));
$red = ($existing['red'] > RED_THESHOLD) ? RED_THESHOLD : $existing['red'];
$green = ($existing['green'] > GREEN_THESHOLD) ? GREEN_THESHOLD : $existing['green'];
$blue = ($existing['blue'] > BLUE_THESHOLD) ? BLUE_THESHOLD : $existing['blue'];
$new = imagecolorexact($image, $red, $green, $blue);
imagesetpixel($image, $x, $y, $new);
}
}
imagepng($image, 'test2.png');
Here is a comparison picture:
I'm trying to convert a grayscale image to pure black and white in PHP using the GD library.
The purpose would be to detect the cervical cells within the image.
I'll leave the PHP code and a MatLab one (I wrote this code in MatLab and I'm trying to obtain the same result in PHP). Basically, I'm having trouble accessing each individual pixel's color and modifying it. sample image
PHP:
<?php
$im = imagecreatefromjpeg("celule.jpg");
function imagetograyscale($im)
{
if (imageistruecolor($im)) {
imagetruecolortopalette($im, false, 256);
}
for ($c = 0; $c < imagecolorstotal($im); $c++) {
$col = imagecolorsforindex($im, $c);
$gray = round(0.299 * $col['red'] + 0.587 * $col['green'] + 0.114 * $col['blue']);
imagecolorset($im, $c, $gray, $gray, $gray);
}
}
imagetograyscale($im);
//imagefilter($im, IMG_FILTER_CONTRAST, -255); //i'm not looking for this effect
header('Content-type: image/jpeg');
imagejpeg($im);
$C = imagesx($im); //width
$L = imagesy($im); //height
echo "Dimensiuni imagine: latime $C, inaltime $L <br>";
//scanning through the image
for($x = 0; $x < $L; $x++) { //each line
for($y = 0; $y < $C; $y++) { //each column
// pixel color at (x, y)
$color = imagecolorat($im, $y, $x);
$color = imagecolorsforindex($im, $color); //getting rgb values
$RED[$x][$y] = $color["red"]; //each rgb component
$GREEN[$x][$y] = $color["green"];
$BLUE[$x][$y] = $color["blue"];
}
}
?>
MATLAB:
clear all, clc, close all;
I = imread('celule.jpg');
imshow(I)
title('original');
a=rgb2gray(I);
figure;
imshow(a)
title('grayscale');
s=size(a);
for i=1:s(1)
for j=1:s(2)
if a(i,j)>190
a(i,j)=0;
else a(i,j)=255;
end
end
end
figure;
imshow(a)
title('pure black and white');
Here's a way to do that with gd:
#!/usr/bin/php -f
<?php
// Open image and get dimensions
$im = imagecreatefromjpeg("cellule.jpg");
$w = imagesx($im);
$h = imagesy($im);
// Convert to greyscale
imagefilter($im,IMG_FILTER_GRAYSCALE);
imagepng($im, "grey.png"); // DEBUG only
// Allocate a new palette image to hold the b&w output
$out = imagecreate($w,$h);
// Allocate b&w palette entries
$black = imagecolorallocate($out,0,0,0);
$white = imagecolorallocate($out,255,255,255);
// Iterate over all pixels, thresholding to pure b&w
for ($x = 0; $x < $w; $x++) {
for ($y = 0; $y < $h; $y++) {
// Get current color
$index = imagecolorat($im, $x, $y);
$grey = imagecolorsforindex($im, $index)['red'];
// Set pixel white if below threshold - don't bother settting black as image is initially black anyway
if ($grey <= 190) {
imagesetpixel($out,$x,$y,$white);
}
}
}
imagepng($out, "result.png");
?>
I've tried experimenting with the GD library to simulate Photoshop's muliply effect, but I haven't found a working solution yet.
According to Wikipedia, the multiply blend mode:
[...] multiplies the numbers for each pixel of the top layer with the corresponding pixel for the bottom layer. The result is a darker picture.
Does anyone know of a way to achieve this using PHP? Any help would be much appreciated.
You need to take every pixel of your image, then multiply each RGB value with your background color / 255 (it's the Photoshop formula). For example, a JPG file with a red background color multiply filter, saved as a PNG file for better results:
<?php
$filter_r=216;
$filter_g=0;
$filter_b=26;
$suffixe="_red";
$path=YOURPATHFILE;
if(is_file($path)){
$image=#imagecreatefromjpeg($path);
$new_path=substr($path,0,strlen($path)-4).$suffixe.".png";
$imagex = imagesx($image);
$imagey = imagesy($image);
for ($x = 0; $x <$imagex; ++$x) {
for ($y = 0; $y <$imagey; ++$y) {
$rgb = imagecolorat($image, $x, $y);
$TabColors=imagecolorsforindex ( $image , $rgb );
$color_r=floor($TabColors['red']*$filter_r/255);
$color_g=floor($TabColors['green']*$filter_g/255);
$color_b=floor($TabColors['blue']*$filter_b/255);
$newcol = imagecolorallocate($image, $color_r,$color_g,$color_b);
imagesetpixel($image, $x, $y, $newcol);
}
}
imagepng($image,$new_path);
}
?>
I've been looking for Multiply blend between two images as well and couldn't find any native-php solution for it. It appears that only way (for now) is to "manually" set pixels, pixel-by-pixel. Here's my code that does Multiply blend between two images, assuming that images are of the same size. You can adjust it to handle different sizes if you like.
function multiplyImage($dst,$src)
{
$ow = imagesx($dst);
$oh = imagesy($dst);
$inv255 = 1.0/255.0;
$c = imagecreatetruecolor($ow,$oh);
for ($x = 0; $x <$ow; ++$x)
{
for ($y = 0; $y <$oh; ++$y)
{
$rgb_src = imagecolorsforindex($src,imagecolorat($src, $x, $y));
$rgb_dst = imagecolorsforindex($dst,imagecolorat($dst, $x, $y));
$r = $rgb_src['red'] * $rgb_dst['red']*$inv255;
$g = $rgb_src['green'] * $rgb_dst['green']*$inv255;
$b = $rgb_src['blue'] * $rgb_dst['blue']*$inv255;
$rgb = imagecolorallocate($c,$r,$g,$b);
imagesetpixel($c, $x, $y, $rgb);
}
}
return $c;
}
Function returns image object so you should ensure to do imagedestroy after you're done using it.
There should be a workaround using overlay native-php blend, which suggests that 50% gray pixels of destination image will be affected by source pixels. In theory, if you do need to blend two black-and-white images (no gray tones), if you set contrast of destination image so white will become 50%-gray, and then overlay-blend source image over it, should give you something similar to multiply. But for color images, or grayscale images, this wouldn't work - above method appears to be the only option.
I was led into this thread when I needed to blend two images in GD. It seems there is no code specifically for that so I will just leave this here for future visitors to this page.
This is a fork from the answer of colivier that supports multiply-blending of two images.
The two images need not be of the same size BUT the overlaying image will be resized and cropped to the size of the bottom layer. I made a fit helper function to do just that but don't bother with that.
imagecolorat returns the base color, even with PNGs with transparency. That is, a 50% black (visible as (128, 128, 128)) will be returned as (0, 0, 0, 64) 64 being the alpha value. This code takes into consideration translucency and converts the translucent colors to the visible color values.
// bottom layer
$img1 = imagecreatefromjpeg(realpath(__DIR__.'/profilePic.jpg'));
// top layer
$img2 = imagecreatefrompng(realpath(__DIR__.'/border2.png'));
imagealphablending($img2, false);
imagesavealpha($img2, true);
$imagex = imagesx($img1);
$imagey = imagesy($img1);
$imagex2 = imagesx($img2);
$imagey2 = imagesy($img2);
// Prereq: Resize img2 to match img1, cropping beyond the aspect ratio
$w1 = max(min($imagex2, $imagex), $imagex);
$h1 = max(min($imagey2, $imagey), $imagey);
$w_using_h1 = round($h1 * $imagex2 / $imagey2);
$h_using_w1 = round($w1 * $imagey2 / $imagex2);
if ($w_using_h1 > $imagex) {
fit($img2, $imagex, $imagey, 'HEIGHT', true);
}
fit($img2, $imagex, $imagey, 'WIDTH', true);
// Actual multiply filter
for ($x = 0; $x < $imagex; ++$x) {
for ($y = 0; $y < $imagey; ++$y) {
$rgb1 = imagecolorat($img1, $x, $y);
$rgb2 = imagecolorat($img2, $x, $y);
$idx1 = imagecolorsforindex($img1, $rgb1);
$idx2 = imagecolorsforindex($img2, $rgb2);
// Shift left 8, then shift right 7
// same as multiply by 256 then divide by 128
// approximate multiply by 255 then divide by 127
// This is basically multiply by 2 but, expanded to show that
// we are adding a fraction of white to the translucent image
// $adder = ($idx2['alpha'] << 8 >> 7);
$adder = ($idx2['alpha'] << 1);
$rmul = min(255, $idx2['red'] + $adder);
$gmul = min(255, $idx2['green'] + $adder);
$bmul = min(255, $idx2['blue'] + $adder);
$color_r = floor($idx1['red'] * $rmul / 255);
$color_g = floor($idx1['green'] * $gmul / 255);
$color_b = floor($idx1['blue'] * $bmul / 255);
$newcol = imagecolorallocatealpha($img1, $color_r, $color_g, $color_b, 0);
imagesetpixel($img1, $x, $y, $newcol);
}
}
imagejpeg($img1, __DIR__.'/out.jpg');
/**
* Fits an image to a $w x $h canvas
*
* #param type $w Target width
* #param type $h Target height
* #param int $fit_which Which dimension to fit
* #param bool $upscale If set to true, will scale a smaller image to fit the given dimensions
* #param bool $padded If set to true, will add padding to achieve given dimensions
*
* #return Image object
*/
function fit(&$img, $w, $h, $fit_which = 'BOTH', $upscale = false, $padded = true) {
if (!in_array($fit_which, array('WIDTH', 'HEIGHT', 'BOTH'))) {
$fit_which = 'BOTH';
}
$w0 = imagesx($img);
$h0 = imagesy($img);
if (!$upscale && $w0 <= $w && $h0 <= $h)
return $this;
if ($padded) {
$w1 = max(min($w0, $w), $w);
$h1 = max(min($h0, $h), $h);
}
else {
$w1 = min($w0, $w);
$h1 = min($h0, $h);
}
$w_using_h1 = round($h1 * $w0 / $h0);
$h_using_w1 = round($w1 * $h0 / $w0);
// Assume width, crop height
if ($fit_which == 'WIDTH') {
$w2 = $w1;
$h2 = $h_using_w1;
}
// Assume height, crop width
elseif ($fit_which == 'HEIGHT') {
$w2 = $w_using_h1;
$h2 = $h1;
}
elseif ($fit_which == 'BOTH') {
if (!$padded) {
$w2 = $w = min($w, $w_using_h1);
$h2 = $h = min($h, $h_using_w1);
}
else {
// Extend vertically
if ($h_using_w1 <= $h) {
$w2 = $w1;
$h2 = $h_using_w1;
}
// Extend horizontally
else {
$w2 = $w_using_h1;
$h2 = $h1;
}
}
}
$im2 = imagecreatetruecolor($w, $h);
imagealphablending($im2, true);
imagesavealpha($im2, true);
$transparent = imagecolorallocatealpha($im2, 255, 255, 255, 127);
imagefill($im2, 0, 0, $transparent);
imagealphablending($img, true);
imagesavealpha($img, true);
// imagefill($im, 0, 0, $transparent);
imagecopyresampled($im2, $img, ($w - $w2) / 2, ($h - $h2) / 2, 0, 0, $w2, $h2, $w0, $h0);
$img = $im2;
}
Have you tried to use php manual?
For people looking to apply a 'multiply' effect on images like the one in Photoshop (generally b&w ones), you can achieve it with the IMG_FILTER_COLORIZE filter.
<?php
function multiplyColor(&$im, $color = array(255, 0, 0)) {
//get opposite color
$opposite = array(255 - $color[0], 255 - $color[1], 255 - $color[2]);
//now we subtract the opposite color from the image
imagefilter($im, IMG_FILTER_COLORIZE, -$opposite[0], -$opposite[1], -$opposite[2]);
}
?>
If used with png image and alpha must be well and works very well
$filter_r=215;
$filter_g=5;
$filter_b=5;
$alpha=70;
$suffixe="_red";
$path="./img/foto_220_590.png";
if(is_file($path)){
$image=imagecreatefrompng($path);
$new_path=substr($path,0,strlen($path)-4).$suffixe.".png";
echo $imagex = imagesx($image);
echo $imagey = imagesy($image);
for ($x = 0; $x <$imagex; ++$x) {
for ($y = 0; $y <$imagey; ++$y) {
$rgb = imagecolorat($image, $x, $y);
$TabColors=imagecolorsforindex ( $image , $rgb );
$color_r=floor($TabColors['red']*$filter_r/255);
$color_g=floor($TabColors['green']*$filter_g/255);
$color_b=floor($TabColors['blue']*$filter_b/255);
//$newcol = imagecolorallocate($image, $color_r,$color_g,$color_b);
// this new alpha
$newcol = imagecolorallocatealpha($image, $color_r,$color_g,$color_b,$alpha);
imagesetpixel($image, $x, $y, $newcol);
}
}
imagepng($image,$new_path);
I updated #colivier script to be able to myltiply two images, and not just an image with a color:
/**
* Multiply $pathToDst and $pathToSrc to $resultPath
*
* #param string $pathToDst
* #param string $pathToSrc
* #param string $resultPath
*/
function multiply($pathToDst, $pathToSrc, $resultPath) {
switch (pathinfo($pathToDst, PATHINFO_EXTENSION)) {
case "gif" :
$resourceDst = imagecreatefromgif($pathToDst);
break;
case "png" :
$resourceDst = imagecreatefrompng($pathToDst);
break;
default :
$resourceDst = imagecreatefromjpeg($pathToDst);
break;
}
switch (pathinfo($pathToSrc, PATHINFO_EXTENSION)) {
case "gif" :
$resourceSrc = imagecreatefromgif($pathToSrc);
break;
case "png" :
$resourceSrc = imagecreatefrompng($pathToSrc);
break;
default :
$resourceSrc = imagecreatefromjpeg($pathToSrc);
break;
}
for ($x = 0; $x < 400; ++$x) {
for ($y = 0; $y < 400; ++$y) {
$TabColorsFlag = imagecolorsforindex($resourceDst, imagecolorat($resourceDst, $x, $y));
$TabColorsPerso = imagecolorsforindex($resourceSrc, imagecolorat($resourceSrc, $x, $y));
$color_r = floor($TabColorsFlag['red'] * $TabColorsPerso['red'] / 255);
$color_g = floor($TabColorsFlag['green'] * $TabColorsPerso['green'] / 255);
$color_b = floor($TabColorsFlag['blue'] * $TabColorsPerso['blue'] / 255);
imagesetpixel($resourceDst, $x, $y, imagecolorallocate($resourceSrc, $color_r, $color_g, $color_b));
}
}
imagepng($resourceDst, $resultPath, 0);
imagedestroy($resourceDst);
imagedestroy($resourceSrc);
}
I have the following PHP method that generates new users a profile image when they first sign up, before they upload their own. All it does is just create them a brightly colored square - something to make the interface look a little more interesting when showing a list of users without profile photos.
How could I adapt this method so it created a checkerboard of random colors? Something like this: http://krazydad.com/bestiary/thumbs/random_pixels.jpg
public function generate_random_image($filename, $w = 200, $h = 200, $chosen_color = NULL) {
if(!$chosen_color) {
$color_options = Array("#6f0247", "#FF0569", "#FFF478", "#BAFFC0", "#27DB2D", "#380470", "#9D69D6");
$random = rand(0,sizeof($color_options));
$chosen_color = $color_options[$random];
}
$rgb = self::hex2rgb($chosen_color);
$image = imagecreatetruecolor($w, $h);
for($row = 1; $row <= $h; $row++) {
for($column = 1; $column <= $w; $column++) {
$color = imagecolorallocate ($image, $rgb[0] , $rgb[1], $rgb[2]);
imagesetpixel($image,$column - 1 , $row - 1, $color);
}
$row_count++;
}
$filename = APP_PATH.$filename;
imagepng($image, $filename);
return $chosen_color;
}
How about you just change
$color = imagecolorallocate ($image, $rgb[0] , $rgb[1], $rgb[2]);
to
$color = imagecolorallocate ($image, rand(0,255), rand(0,255), rand(0,255));
Then, each pixel will have it's own colour. Just draw to a small image, then scale by 200% or 300% (or some other arbitrary number) and you'll get nice, big chunky pixels like the image you linked.
While iterating through $rows and $columns you should increase step to desired pixel size and choose another color with each iteration.
example for pixel width = 20x20 :
$pixel = 20;
for($row = 0; $row <= $h / $pixel; $row++) {
for($column = 0; $column <= $w/ $pixel; $column++) {
$rgb = self::hex2rgb($color_options[rand(0,sizeof($color_options))]);
$color = imagecolorallocate ($image, $rgb[0] , $rgb[1], $rgb[2]);
imagefilledrectangle(
$image,
$column*$pixel,
$row*pixel,
$column*$pixel+$pixel,
$row*pixel+$pixel,
$color
);
}
}
Does anyone know how to achieve this?
I am assuming from your tags that you mean to flip a GD image.
Do you mean flip as in rotate? That can be done using imagerotate:
Rotates the image image using the given angle in degrees.
The center of rotation is the center of the image, and the rotated image may have different dimensions than the original image.
Or do you mean mirror an image? There's no method for that out of the box, but maybe this code snippet helps. (It not very performant, though, because it copies pixel by pixel.)
For fast advanced image editing operations, ImageMagick is the best tool around. If you are on shared hosting, it needs to be installed by your provider to work.
You can use some kind of font-substitution trickery like here, or you can use the PHP version of ImageMagick.
Untested... but this seems like it ought to work, composed of other gd functions (maybe slowly):
function flipImageHorizontal($im){
$width = imagesx($im);
$height = imagesy($im);
for($y = 0; $y < $height; $y++){ // for each column
for($x = 0; $x < ($width >> 1); $x++){ // for half the pixels in the row
// get the color on the left side
$rgb = imagecolorat($im, $x, $y);
$colors = imagecolorsforindex($im, $rgb);
$current_color = imagecolorallocate($im, $colors["red"], $colors["green"], $colors["blue"]);
// get the color on the right side (mirror)
$rgb = imagecolorat($im, $width - $x, $y);
$colors = imagecolorsforindex($im, $rgb);
$mirror_color = imagecolorallocate($im, $colors["red"], $colors["green"], $colors["blue"]);
// swap the colors
imagesetpixel($im, $x, $y, $mirror_color);
imagesetpixel($im, $width - $x, $y, $color);
}
}
}
function flipImageVertical($im){
$width = imagesx($im);
$height = imagesy($im);
for($x = 0; $x < $width; $x++){ // for each row
for($y = 0; $y < ($height >> 1); $y++){ // for half the pixels in the col
// get the color on the top
$rgb = imagecolorat($im, $x, $y);
$colors = imagecolorsforindex($im, $rgb);
$current_color = imagecolorallocate($im, $colors["red"], $colors["green"], $colors["blue"]);
// get the color on the bottom (mirror)
$rgb = imagecolorat($im, $x, $height - $y);
$colors = imagecolorsforindex($im, $rgb);
$mirror_color = imagecolorallocate($im, $colors["red"], $colors["green"], $colors["blue"]);
// swap the colors
imagesetpixel($im, $x, $y, $mirror_color);
imagesetpixel($im, $x, $height - $y, $color);
}
}
}
So you could use bool imagestring ( resource $image , int $font , int $x , int $y , string $string , int $color ) to create an image from a text string, then run it through the appropriate flip function that I've written above...
To add vertical text to an existing image in PHP, use function
imagettftext($im, 10, $angle, $x, $y, $black, $font, $text);
With $angle = 90, the text will be vertical.
Example:
http://www.php.net/manual/en/function.imagettfbbox.php#refsect1-function.imagettfbbox-returnvalues
Hint:
The example uses $angle = 45, so text is diagonal on the image
Maybe something as simple as this?
function toVertical ($string)
{
foreach (str_split($string) as $letter)
{
$newStr.="$letter\n";
}
return $newStr;
}
function toHorizontal($string)
{
foreach(explode("\n",$string) as $letter)
{
$newStr.=$letter;
}
return $newStr;
}
$v = toVertical("This string should be printed vertically");
echo $v;
$h = toHorizontal($v);
echo $h;
---------- PHP Execute ----------
T
h
i
s
s
t
r
i
n
g
s
h
o
u
l
d
b
e
p
r
i
n
t
e
d
v
e
r
t
i
c
a
l
l
y
This string should be printed vertically
Output completed (0 sec consumed)