Reuse color ramp memorry placement when already available

mapbox · May 15, 2020 · 13779a5 · 13779a5
1 parent 8d83283
commit 13779a5
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Showing 3 changed files with 75 additions and 9 deletions.
diff --git a/src/style/style_layer/line_style_layer.js b/src/style/style_layer/line_style_layer.js
@@ -73,7 +73,7 @@ class LineStyleLayer extends StyleLayer {
         const maxTilePixelSize = 1024;
         const maxTextureCoverage = geometryTileCoverageAtMaxZoom * maxTilePixelSize;
         const textureResolution = nextPowerOfTwo(clamp(maxTextureCoverage, 256, maxTextureSize));
-        this.gradient = renderColorRamp(expression, 'lineProgress', this.stepInterpolant ? textureResolution : 256);
+        this.gradient = renderColorRamp(expression, 'lineProgress', this.stepInterpolant ? textureResolution : 256, this.gradient || undefined);
     }
 
     recalculate(parameters: EvaluationParameters, availableImages: Array<string>) {

diff --git a/src/util/color_ramp.js b/src/util/color_ramp.js
@@ -12,20 +12,28 @@ import type {StylePropertyExpression} from '../style-spec/expression/index';
  *
  * @private
  */
-export default function renderColorRamp(expression: StylePropertyExpression, colorRampEvaluationParameter: string, textureResolution?: number): RGBAImage {
+export default function renderColorRamp(expression: StylePropertyExpression, colorRampEvaluationParameter: string, textureResolution?: number, image?: RGBAImage): RGBAImage {
     const resolution = textureResolution || 256;
     assert(isPowerOfTwo(resolution));
-    const colorRampData = new Uint8Array(resolution * 4);
+    let outImage;
+
+    if (image && image.width === resolution) {
+        outImage = image;
+    } else {
+        outImage = new RGBAImage({width: resolution, height: 1});
+    }
+
     const evaluationGlobals = {};
     for (let i = 0, j = 0; i < resolution; i++, j += 4) {
         evaluationGlobals[colorRampEvaluationParameter] = i / (resolution - 1);
         const pxColor = expression.evaluate((evaluationGlobals: any));
         // the colors are being unpremultiplied because Color uses
         // premultiplied values, and the Texture class expects unpremultiplied ones
-        colorRampData[j + 0] = Math.floor(pxColor.r * 255 / pxColor.a);
-        colorRampData[j + 1] = Math.floor(pxColor.g * 255 / pxColor.a);
-        colorRampData[j + 2] = Math.floor(pxColor.b * 255 / pxColor.a);
-        colorRampData[j + 3] = Math.floor(pxColor.a * 255);
+        outImage.data[j + 0] = Math.floor(pxColor.r * 255 / pxColor.a);
+        outImage.data[j + 1] = Math.floor(pxColor.g * 255 / pxColor.a);
+        outImage.data[j + 2] = Math.floor(pxColor.b * 255 / pxColor.a);
+        outImage.data[j + 3] = Math.floor(pxColor.a * 255);
     }
-    return new RGBAImage({width: resolution, height: 1}, colorRampData);
+
+    return outImage;
 }
diff --git a/test/unit/util/color_ramp.test.js b/test/unit/util/color_ramp.test.js
@@ -21,7 +21,7 @@ function nearlyEquals(a, b) {
     return a.every((e, i) => Math.abs(e - b[i]) <= 3);
 }
 
-test('renderColorRamp', (t) => {
+test('renderColorRamp linear', (t) => {
 
     const expression = createPropertyExpression([
         'interpolate',
@@ -47,3 +47,61 @@ test('renderColorRamp', (t) => {
 
     t.end();
 });
+
+test('renderColorRamp step', (t) => {
+
+    const expression = createPropertyExpression([
+        'step',
+        ['line-progress'],
+        'rgba(0, 0, 255, 0.1)',
+        0.1, 'red',
+        0.2, 'yellow',
+        0.3, 'white',
+        0.5, 'black',
+        1, 'black'
+    ], spec, {handleErrors: false}).value;
+
+    const ramp = renderColorRamp(expression, 'lineProgress', 512);
+
+    t.equal(ramp.width, 512);
+    t.equal(ramp.height, 1);
+
+    t.equal(pixelAt(ramp, 0)[3], 25, 'pixel at 0.0 matches input alpha');
+    t.ok(nearlyEquals(pixelAt(ramp, 50), [0, 0, 255, 25]), 'pixel < 0.1 matches input');
+    t.ok(nearlyEquals(pixelAt(ramp, 53), [255, 0, 0, 255]), 'pixel > 0.1 & < 0.2 matches input');
+    t.ok(nearlyEquals(pixelAt(ramp, 103), [255, 255, 0, 255]), 'pixel > 0.2 & < 0.3 matches input');
+    t.ok(nearlyEquals(pixelAt(ramp, 160), [255, 255, 255, 255]), 'pixel > 0.3 & < 0.5 matches input');
+    t.ok(nearlyEquals(pixelAt(ramp, 256), [0, 0, 0, 255]), 'pixel > 0.5 matches input');
+
+    t.end();
+});
+
+test('renderColorRamp usePlacement', (t) => {
+
+    const expression = createPropertyExpression([
+        'step',
+        ['line-progress'],
+        'rgba(255, 0, 0, 0.5)',
+        0.1, 'black',
+        0.2, 'red',
+        0.3, 'blue',
+        0.5, 'white',
+        1, 'white'
+    ], spec, {handleErrors: false}).value;
+
+    let ramp = renderColorRamp(expression, 'lineProgress', 512);
+
+    t.equal(ramp.width, 512);
+    t.equal(ramp.height, 1);
+
+    ramp = renderColorRamp(expression, 'lineProgress', 512, ramp);
+
+    t.equal(pixelAt(ramp, 0)[3], 127, 'pixel at 0.0 matches input alpha');
+    t.ok(nearlyEquals(pixelAt(ramp, 50), [255, 0, 0, 127]), 'pixel < 0.1 matches input');
+    t.ok(nearlyEquals(pixelAt(ramp, 53), [0, 0, 0, 255]), 'pixel > 0.1 & < 0.2 matches input');
+    t.ok(nearlyEquals(pixelAt(ramp, 103), [255, 0, 0, 255]), 'pixel > 0.2 & < 0.3 matches input');
+    t.ok(nearlyEquals(pixelAt(ramp, 160), [0, 0, 255, 255]), 'pixel > 0.3 & < 0.5 matches input');
+    t.ok(nearlyEquals(pixelAt(ramp, 256), [255, 255, 255, 255]), 'pixel > 0.5 matches input');
+
+    t.end();
+});