/
grayscale.ts
60 lines (54 loc) · 1.88 KB
/
grayscale.ts
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/*
* Copyright (c) 2016-present Invertase Limited
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this library except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import * as superstruct from 'superstruct';
import * as utils from '../utils';
import { OperationBuilder } from '../types';
/**
* The user visible name of this operation.
*/
const name = 'grayscale';
/**
* Convert to 8-bit grayscale; 256 shades of grey.
* This is a linear operation.
* If the input image is in a non-linear colour space such as sRGB,
* use gamma() with grayscale() for the best results.
* By default the output image will be web-friendly sRGB and contain
* three (identical) color channels.
* This may be overridden by other sharp operations such as toColourspace('b-w'),
* which will produce an output image containing one color channel.
* An alpha channel may be present, and will be unchanged by the operation.
*/
const struct = superstruct.object({
operation: superstruct.literal(name),
/**
* Convert to grayscale, true or false value. Defaults to true.
*/
grayscale: superstruct.defaulted(utils.coerceStringToBoolean(), true),
});
export type OperationGrayScale = superstruct.Infer<typeof struct>;
export const operationGrayScale: OperationBuilder = {
name,
struct,
build(operation) {
const options = operation.options as OperationGrayScale;
return [
{
method: name,
arguments: [options.grayscale],
},
];
},
};