我尝试使用GD库在PHP中将灰度图像转换为纯黑白。
目的是检测图像内的宫颈细胞。
我会留下PHP代码和一个MatLab代码（我在MatLab中编写了这段代码，并试图在PHP中获得相同的结果）。基本上，我在访问每个像素的颜色并修改它时遇到了麻烦。sample image
PHP语言：

<?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语言：

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');