mapbox-gl-js/debug/raster-blend-modes.html at d8445d9ab0675f3cca4aec1110c7966b06e32f33 · mapbox/mapbox-gl-js · GitHub

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<!DOCTYPE html>
<html>
<head>
    <title>Raster Blend Modes Test - Mapbox GL JS</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="../dist/mapbox-gl.css" />
    <style>
        body {
            margin: 0;
            padding: 0;
            font-family: Arial, sans-serif;
        }
        #map {
            position: absolute;
            top: 0;
            bottom: 0;
            width: 100%;
        }
        #controls {
            position: fixed;
            top: 10px;
            left: 10px;
            background: white;
            padding: 20px;
            border-radius: 8px;
            box-shadow: 0 2px 8px rgba(0,0,0,0.3);
            z-index: 1;
            max-width: 350px;
        }
        #controls h3 {
            margin: 0 0 15px 0;
        }
        .control-group {
            margin-bottom: 20px;
        }
        .control-group label {
            display: block;
            font-weight: bold;
            margin-bottom: 8px;
        }
        .button-group {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 8px;
        }
        button {
            padding: 10px;
            border: 2px solid #2196F3;
            background: white;
            border-radius: 4px;
            cursor: pointer;
            font-weight: bold;
            transition: all 0.2s;
        }
        button:hover {
            background: #e3f2fd;
        }
        button.active {
            background: #2196F3;
            color: white;
        }
        .slider-group {
            margin-top: 10px;
        }
        .slider-group input {
            width: 100%;
            margin-top: 5px;
        }
        .value-display {
            text-align: right;
            color: #666;
            font-size: 14px;
        }
        #info {
            margin-top: 15px;
            padding: 15px;
            background: #f5f5f5;
            border-radius: 4px;
            font-size: 13px;
        }
        #info .current {
            font-weight: bold;
            color: #2196F3;
            margin-bottom: 8px;
        }
        #info .expected {
            color: #666;
            line-height: 1.6;
        }
        .debug {
            margin-top: 10px;
            padding: 10px;
            background: #fff3cd;
            border-radius: 4px;
            font-size: 11px;
            font-family: monospace;
        }
    </style>
</head>

<body>
<div id="map"></div>

<div id="controls">
    <h3>Raster Blend Modes</h3>
    <p style="margin: 0 0 15px 0; font-size: 12px; color: #666;">
        WebGL blend functions with neutral color blending. Zero performance overhead.<br>
        <strong>Layers:</strong> Satellite (base) + OSM overlay (top, with blend mode applied)
    </p>

    <div class="control-group">
        <label>Blend Mode:</label>
        <div class="button-group">
            <button id="btn-normal" class="active">Normal</button>
            <button id="btn-multiply">Multiply</button>
            <button id="btn-screen">Screen</button>
            <button id="btn-darken">Darken</button>
            <button id="btn-lighten">Lighten</button>
        </div>
    </div>

    <div class="control-group">
        <label>OSM Layer Opacity:</label>
        <input type="range" id="opacity-slider" min="0" max="1" step="0.1" value="0.7">
        <div class="value-display">Current: <span id="opacity-value">0.7</span></div>
        <p style="margin: 5px 0 0 0; font-size: 11px; color: #999;">
            Controls opacity of the OSM overlay layer (top layer)
        </p>
    </div>

    <div id="info">
        <div class="current">Current: <span id="current-mode">normal</span> @ <span id="current-opacity">0.7</span></div>
        <div class="expected" id="expected-text">
            Standard alpha blending. OSM layer semi-transparent over satellite imagery.
        </div>
    </div>

    <div class="debug">
        <strong>Debug Info:</strong><br>
        Shader premultiply: <span id="debug-premult">?</span><br>
        Actual blend mode: <span id="debug-blend">?</span><br>
        Actual opacity: <span id="debug-opacity">?</span>
    </div>

    <div class="debug" id="validation-warning" style="display: none; background: #ffebee; border: 1px solid #f44336;">
        <strong style="color: #f44336;">⚠️ Compatibility Warning:</strong><br>
        <span id="warning-text"></span>
    </div>

    <div class="debug" style="background: #e3f2fd; border: 1px solid #2196F3;">
        <strong style="color: #2196F3;">📍 Map Position:</strong><br>
        Center: <span id="map-center">-122.2129, 37.5047</span><br>
        Zoom: <span id="map-zoom">13.68</span><br>
        <small style="color: #666;">Move the map to find interesting areas!</small>
    </div>
</div>

<script src="../dist/mapbox-gl-dev.js"></script>
<script type="module">
import {getAccessToken} from './access_token_generated.js';

mapboxgl.accessToken = getAccessToken();

const expectedText = {
    'normal': 'Standard alpha blending (NO blend mode set). Uses only raster-opacity for transparency. This is the default behavior when raster-blend-mode is not specified.',
    'multiply': 'MULTIPLY (✓ Excellent): Darkens the image. Uses neutral color blending toward white. Note: Middle opacity values (0.3-0.7) appear BRIGHTER than expected due to blending toward white before multiplication. This is expected behavior, not a bug.',
    'screen': 'SCREEN (✓ Excellent): Lightens the image. Uses neutral color blending toward black. Note: Similar non-linear brightness behavior as multiply - middle opacity values show reduced lightening effect.',
    'darken': 'DARKEN (⚠️ Limited): Shows darker pixels (MIN operation). WARNING: Limited opacity support - opacity only affects alpha channel, not RGB blending. Use MULTIPLY instead for opacity-controlled darkening.',
    'lighten': 'LIGHTEN (✓ Excellent): Shows lighter pixels (MAX operation). Uses neutral color blending toward black. Provides most intuitive opacity behavior of all blend modes.'
};

const map = new mapboxgl.Map({
    container: 'map',
    style: {
        version: 8,
        sources: {
            'satellite': {
                type: 'raster',
                url: 'mapbox://mapbox.satellite',
                tileSize: 256
            },
            'osm': {
                type: 'raster',
                tiles: ['https://tile.openstreetmap.org/{z}/{x}/{y}.png'],
                tileSize: 256,
                attribution: '&copy; OpenStreetMap'
            }
        },
        layers: [
            {
                id: 'background',
                type: 'background',
                paint: {
                    'background-color': '#000'
                }
            },
            {
                id: 'satellite',
                type: 'raster',
                source: 'satellite'
            },
            {
                id: 'osm-overlay',
                type: 'raster',
                source: 'osm',
                paint: {
                    'raster-opacity': 0.7
                    // No raster-blend-mode set = standard alpha blending
                }
            }
        ]
    },
    center: [-122.2129, 37.5047], // San Francisco Bay Area
    zoom: 13.68
});

// Add navigation controls
map.addControl(new mapboxgl.NavigationControl(), 'top-right');

let currentMode = 'normal';
let currentOpacity = 0.7;

function updateDebugInfo() {
    // Check if layer exists before accessing it
    if (!map.getLayer('osm-overlay')) {
        return;
    }

    const blendMode = map.getPaintProperty('osm-overlay', 'raster-blend-mode');
    const opacity = map.getPaintProperty('osm-overlay', 'raster-opacity');
    const isPremult = !blendMode ? 1.0 : 0.0;

    document.getElementById('debug-blend').textContent = blendMode || '(not set)';
    document.getElementById('debug-opacity').textContent = opacity;
    document.getElementById('debug-premult').textContent = isPremult;

    // Show validation warning for darken with opacity !== 0 or 1
    const warningDiv = document.getElementById('validation-warning');
    const warningText = document.getElementById('warning-text');

    if (blendMode === 'darken' && opacity !== 0 && opacity !== 1) {
        warningText.textContent = `⚠️ DARKEN has limited opacity support. RGB blending remains at full strength (only alpha changes). For opacity-controlled darkening, use MULTIPLY instead. See console for details.`;
        warningDiv.style.display = 'block';
    } else {
        warningDiv.style.display = 'none';
    }
}

function setBlendMode(mode) {
    if (!map.getLayer('osm-overlay')) {
        console.warn('Layer not ready yet');
        return;
    }

    currentMode = mode;

    // For 'normal', remove the blend mode property entirely (uses only opacity)
    if (mode === 'normal') {
        // Remove the property to use standard alpha blending
        map.setPaintProperty('osm-overlay', 'raster-blend-mode', undefined);
    } else {
        map.setPaintProperty('osm-overlay', 'raster-blend-mode', mode);
    }

    // Update UI
    document.querySelectorAll('.button-group button').forEach(btn => {
        btn.classList.remove('active');
    });
    document.getElementById(`btn-${mode}`).classList.add('active');

    document.getElementById('current-mode').textContent = mode;
    document.getElementById('expected-text').textContent = expectedText[mode];

    updateDebugInfo();

    console.log(`Blend mode changed to: ${mode} @ opacity ${currentOpacity}`);
}

function setOpacity(value) {
    if (!map.getLayer('osm-overlay')) {
        console.warn('Layer not ready yet');
        return;
    }

    currentOpacity = value;
    map.setPaintProperty('osm-overlay', 'raster-opacity', parseFloat(value));

    document.getElementById('opacity-value').textContent = value;
    document.getElementById('current-opacity').textContent = value;

    updateDebugInfo();
}

// Blend mode buttons
document.getElementById('btn-normal').addEventListener('click', () => setBlendMode('normal'));
document.getElementById('btn-multiply').addEventListener('click', () => setBlendMode('multiply'));
document.getElementById('btn-screen').addEventListener('click', () => setBlendMode('screen'));
document.getElementById('btn-darken').addEventListener('click', () => setBlendMode('darken'));
document.getElementById('btn-lighten').addEventListener('click', () => setBlendMode('lighten'));

// Opacity slider
document.getElementById('opacity-slider').addEventListener('input', (e) => {
    setOpacity(e.target.value);
});

// Keyboard shortcuts
document.addEventListener('keydown', (e) => {
    if (e.key === '1') setBlendMode('normal');
    if (e.key === '2') setBlendMode('multiply');
    if (e.key === '3') setBlendMode('screen');
    if (e.key === '4') setBlendMode('darken');
    if (e.key === '5') setBlendMode('lighten');
});

map.on('load', () => {
    console.log('Map loaded successfully');
    updateDebugInfo();
    console.log('═══════════════════════════════════════════════════════');
    console.log('  Mapbox GL JS - Raster Blend Modes Test');
    console.log('═══════════════════════════════════════════════════════');
    console.log('Controls:');
    console.log('  • Click buttons to change blend mode');
    console.log('  • Use slider to change opacity');
    console.log('  • Keyboard: 1=Normal, 2=Multiply, 3=Screen, 4=Darken, 5=Lighten');
    console.log('');
    console.log('Expected Behavior:');
    console.log('  • MULTIPLY/SCREEN: Non-linear brightness at middle opacity');
    console.log('    (This is expected - blends toward neutral color)');
    console.log('  • LIGHTEN: Excellent opacity support, most intuitive');
    console.log('  • DARKEN: Limited opacity support (use multiply instead)');
    console.log('');
    console.log('Implementation: Neutral color blending (zero overhead)');
    console.log('  multiply → white, screen → black, lighten → black');
    console.log('  darken → no neutral (direct output)');
    console.log('═══════════════════════════════════════════════════════');
});

map.on('idle', () => {
    updateDebugInfo();
});

// Update map position display
function updateMapPosition() {
    const center = map.getCenter();
    const zoom = map.getZoom();
    document.getElementById('map-center').textContent =
        `${center.lng.toFixed(4)}, ${center.lat.toFixed(4)}`;
    document.getElementById('map-zoom').textContent = zoom.toFixed(2);
}

map.on('move', updateMapPosition);
map.on('zoom', updateMapPosition);
map.on('load', updateMapPosition);

</script>
</body>
</html>