Image watermark

An image drawn behind the chart content, as a series primitive (ImageWatermark) or as a pane primitive (ImageWatermarkPane). The image is placed within the pane — centered by default, or anchored to a corner — and scaled to fit, to fill, or not at all. Position, size limits, padding, opacity and visibility can all be changed after the watermark has been attached.

The series primitive belongs to the series it is attached to: it lives in that series' pane and is removed together with the series. The pane primitive needs no series at all.

Use it to brand a chart with a logo, or to mark a chart as a preview or draft, without touching the chart's own rendering.

Lightweight Charts™ 5 also ships a built-in image watermark. createImageWatermark(pane, url, options) is a pane primitive which centers an image and scales it to fit. If that is all you need, the built-in function is the right choice. Use this package for a watermark tied to a specific series rather than to a pane, or for anything the built-in does not offer: corner and fractional positions, objectFit, crossOrigin, visible, zOrder, applyOptions / setImage and an onError callback.

Usage​

Behind a series​

Create the watermark with the image URL, then attach it to the series it should follow:

import { createChart, LineSeries } from 'lightweight-charts';
import { ImageWatermark } from '@tradingview/lwc-plugin-image-watermark';

const chart = createChart(document.getElementById('container'));
const series = chart.addSeries(LineSeries);
series.setData(data);

const watermark = new ImageWatermark('/logo.svg', {
    maxHeight: 400,
    maxWidth: 400,
    padding: 50,
    alpha: 0.4,
});
series.attachPrimitive(watermark);

To remove the watermark, detach it from the series:

series.detachPrimitive(watermark);

Behind a pane​

ImageWatermarkPane takes the same image URL and the same options, and is attached to a pane instead of a series. Use it when the watermark should stay put while series are added and removed:

import { ImageWatermarkPane } from '@tradingview/lwc-plugin-image-watermark';

const watermark = new ImageWatermarkPane('/logo.svg', { alpha: 0.4 });
chart.panes()[0].attachPrimitive(watermark);

// later
chart.panes()[0].detachPrimitive(watermark);

Changing the watermark​

Both classes have the same methods:

watermark.applyOptions({ position: 'bottom-right', alpha: 0.2 });
watermark.setImage('/other-logo.svg'); // same as applyOptions({ imageUrl })
watermark.options(); // the current options, with the defaults filled in

applyOptions merges: an option which is not passed, or is passed as undefined, is left unchanged.

The image is loaded when the primitive is attached and drawn once it has decoded; until then nothing is rendered. Any URL the browser can load into an <img> element works, including SVG and data URLs. Decoded images are cached by URL, so detaching and re-attaching a watermark — or using the same image twice — never loads it again.

Options​

Options are passed as the second constructor argument, which is optional, as is every option in it. The type is ImageWatermarkPluginOptions, and the defaults are exported as defaultOptions.

Position and size​

The drawing area is the pane inset by padding and limited to maxWidth / maxHeight. position places that area within the pane and the image within that area:

• a named anchor — 'center' or one of the four corners;
• { x, y }, fractions of the free space from 0 to 1. { x: 0, y: 0 } is the top-left corner, { x: 1, y: 1 } the bottom-right one, { x: 0.5, y: 0 } the middle of the top edge. Values outside 0…1 are clamped.

objectFit then decides the scale. With 'contain' (the default) the image is scaled up or down to fit, keeping its aspect ratio; set maxWidth / maxHeight to its natural size if it should never be enlarged. With 'cover' it is scaled to fill the drawing area and the overflow is cropped, and with 'none' it is drawn at its natural size. Nothing is ever drawn outside the drawing area, so padding always holds.

Notes​

• The watermark is drawn behind the chart content by default: the grid, the series, and other primitives all appear on top of it. Only the pane background is below it. Pass zOrder: 'top' to draw it over everything instead.
• The image appears only in the pane it belongs to, where the series is drawn. It never covers the price scales or the time scale, and a visible left price scale or a second pane does not move it.
• A watermark whose image cannot be loaded draws nothing and throws nothing. Pass onError to be told about it; the plugin logs nothing itself.
• ImageWatermarkOptions is still exported, as a deprecated alias of ImageWatermarkPluginOptions. The plugin option type was renamed because the library exports an ImageWatermarkOptions of its own, for the built-in createImageWatermark. The alias is kept for compatibility and will be removed in a future major version.
• The image can be loaded from any origin. However, an image served without CORS headers marks the canvas as "tainted", and takeScreenshot fails on a tainted canvas. If you plan to export the chart as an image, serve the watermark image with CORS headers and set crossOrigin: 'anonymous'.