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<?php

unlink('scatter00.png');
require_once ('../jpgraph/jpgraph.php');
require_once ('../jpgraph/jpgraph_scatter.php');
// Function to calculate ΔE₀₀ (CIEDE2000)
include 'de00.php';
// Center color (L*, a*, b*)
// Center color (L*, a*, b*)
$L_center = 89;
$a_center = -5;
$b_center = 93;

// Generate points for 2 ΔE₀₀ ellipse/circle
$a_values_00 = [];
$b_values_00 = [];
for ($angle = 0; $angle <= 360; $angle += 5) { // Adjust step size for more/less precision
    // Initial guess for a* and b* (using ΔE76 circle as a starting point)
    $a_guess = $a_center + 2 * cos(deg2rad($angle));
    $b_guess = $b_center + 2 * sin(deg2rad($angle));

    // Refine the guess to achieve ΔE₀₀ ≈ 2
    $tolerance = 0.01;
    do {
        $deltaE = de00($L_center, $a_center, $b_center, $L_center, $a_guess, $b_guess);

        // Adjust a_guess and b_guess
        $a_guess += 0.01 * (2 - $deltaE) * cos(deg2rad($angle));
        $b_guess += 0.01 * (2 - $deltaE) * sin(deg2rad($angle));
    } while (abs($deltaE - 2) > $tolerance);

    // Save the point
    $a_values_00[] = $a_guess;
    $b_values_00[] = $b_guess;
}

// Generate points for 2 ΔE₇₆ circle
$a_values_76 = [];
$b_values_76 = [];
for ($angle = 0; $angle <= 360; $angle += 5) { // Adjust step size for more/less precision
    $a_values_76[] = $a_center + 2 * cos(deg2rad($angle));
    $b_values_76[] = $b_center + 2 * sin(deg2rad($angle));
}

$min_a = min(min($a_values_00), min($a_values_76)) - 0;
$max_a = max(max($a_values_00), max($a_values_76)) + 0;
$min_b = min(min($b_values_00), min($b_values_76)) - 0;
$max_b = max(max($b_values_00), max($b_values_76)) + 0;

$range = max(($max_a - $min_a), ($max_b - $min_b));
//echo "range=".$range.",a range:".($max_a - $min_a).",b range:".($max_b - $min_b);
// Ensure the scale is square
$ratio=($max_a - $min_a)/($max_b - $min_b);
//echo "ratio=".$ratio;

// Create a square graph (1:1 aspect ratio)
$graphWidth = 600*$ratio;
$graphHeight = 600;
$graph = new Graph($graphWidth, $graphHeight);

// Set the scale to ensure equal scaling for x and y axes

$graph->SetScale('linlin', $min_b, $max_b, $min_a, $max_a);
// Set equal tick intervals for both axes
/* $interval = $range / 10;
$graph->xaxis->SetTickPositions(range($min_a, $max_a, $interval));
$graph->yaxis->SetTickPositions(range($min_b, $max_b, $interval));
// Force equal scaling for X and Y axes
//$graph->SetScale('linlin', $min_a, $max_a, $min_b, $max_b);
$graph->SetBox(true); // Add a box around the graph
$graph->SetFrame(true); // Add a frame around the graph
 */
// Set titles
//$graph->title->Set('2 ΔE00 Ellipse and 2 ΔE00 Circle');
$graph->xaxis->title->Set('a*');
$graph->yaxis->title->Set('b*');

// Create scatter plots
$scatter_00 = new ScatterPlot($b_values_00, $a_values_00);
$scatter_00->mark->SetType(MARK_FILLEDCIRCLE);
$scatter_00->mark->SetWidth(5);
$scatter_00->mark->SetColor('blue');
$scatter_00->SetLegend('2 ΔE00');

$scatter_76 = new ScatterPlot($b_values_76, $a_values_76);
$scatter_76->mark->SetType(MARK_FILLEDCIRCLE);
$scatter_76->mark->SetWidth(5);
$scatter_76->mark->SetColor('red');
$scatter_76->SetLegend('2 ΔE');

// Add the plots to the graph
$graph->Add($scatter_00);
$graph->Add($scatter_76);

// Display the graph
$graph->Stroke('scatter00.png');

?>
<img src="scatter00.png">
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