raster identity fill shorthand

README.md

@@ -1564,7 +1564,7 @@ Returns a new link with the given *data* and *options*.
 [Source](./src/marks/raster.js) · [Examples](https://observablehq.com/@observablehq/plot-raster) · Renders a raster image from spatial samples. If data is provided, it represents discrete samples in abstract coordinates *x* and *y*; the *fill* and *fillOpacity* channels specify further abstract values (_e.g._, height in a topographic map) to be [spatially interpolated](#spatial-interpolation) to produce an image.
 
 ```js
-Plot.raster(volcano.values, {width: volcano.width, height: volcano.height, fill: Plot.identity})
+Plot.raster(volcano.values, {width: volcano.width, height: volcano.height})
 ```
 
 The *fill* and *fillOpacity* channels may alternatively be specified as continuous functions *f*(*x*, *y*) to be evaluated at each pixel centroid of the raster grid (without interpolation).

src/marks/contour.js

@@ -188,7 +188,7 @@ function contourGeometry({thresholds, interval, ...options}) {
 }
 
 export function contour() {
-  return new Contour(...maybeTuples(...arguments));
+  return new Contour(...maybeTuples("value", ...arguments));
 }
 
 function finiteExtent(VV) {

src/marks/raster.js

@@ -1,7 +1,7 @@
 import {blurImage, Delaunay, randomLcg, rgb} from "d3";
 import {valueObject} from "../channel.js";
 import {create} from "../context.js";
-import {map, first, second, third, isTuples, isNumeric, isTemporal, take} from "../options.js";
+import {map, first, second, third, isTuples, isNumeric, isTemporal, take, identity} from "../options.js";
 import {Mark} from "../plot.js";
 import {applyAttr, applyDirectStyles, applyIndirectStyles, applyTransform, impliedString} from "../style.js";
 import {initializer} from "../transforms/basic.js";
@@ -165,23 +165,29 @@ export class Raster extends AbstractRaster {
   }
 }
 
-export function maybeTuples(data, options) {
-  if (arguments.length < 2) (options = data), (data = null);
-  let {x, y, fill, ...rest} = options;
-  // Because we implicit x and y when fill is a function of (x, y), and when
+export function maybeTuples(k, data, options) {
+  if (arguments.length < 3) (options = data), (data = null);
+  let {x, y, [k]: z, ...rest} = options;
+  // Because we use implicit x and y when z is a function of (x, y), and when
   // data is a dense grid, we must further disambiguate by testing whether data
   // contains [x, y, z?] tuples. Hence you can’t use this shorthand with a
   // transform that lazily generates tuples, but that seems reasonable since
   // this is just for convenience anyway.
   if (x === undefined && y === undefined && isTuples(data)) {
     (x = first), (y = second);
-    if (fill === undefined) fill = third;
+    if (z === undefined) z = third;
   }
-  return [data, {...rest, x, y, fill}];
+  return [data, {...rest, x, y, [k]: z}];
 }
 
 export function raster() {
-  return new Raster(...maybeTuples(...arguments));
+  const [data, options] = maybeTuples("fill", ...arguments);
+  return new Raster(
+    data,
+    data == null || options.fill !== undefined || options.fillOpacity !== undefined
+      ? options
+      : {...options, fill: identity}
+  );
 }
 
 // See rasterBounds; this version is called during render.