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Code Issues Releases Wiki Activity

PngParser: Add support for tIME chunk.

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This commit is contained in:
Jeff Schiller 2024-01-18 19:48:18 -08:00
parent 9f5b3a4882
commit 1869cd7bfa
3 changed files with 65 additions and 3 deletions
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53
image/parsers/png.js
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@ -14,7 +14,7 @@ import { ByteStream } from '../../io/bytestream.js';
// https://www.w3.org/TR/png-3/
// https://en.wikipedia.org/wiki/PNG#File_format
// TODO: Ancillary chunks eXIf, hIST, pHYs, sPLT, tIME.
// TODO: Ancillary chunks eXIf, hIST, pHYs, sPLT.
// let DEBUG = true;
let DEBUG = false;
@ -34,6 +34,7 @@ export const PngParseEventType = {
iTXt: 'intl_text_data',
sBIT: 'significant_bits',
tEXt: 'textual_data',
tIME: 'last_mod_time',
tRNS: 'transparency',
zTXt: 'compressed_textual_data',
};
@ -242,6 +243,25 @@ export class PngBackgroundColorEvent extends Event {
}
}
/**
* @typedef PngLastModTime
* @property {number} year Four-digit year.
* @property {number} month One-based. Value from 1-12.
* @property {number} day One-based. Value from 1-31.
* @property {number} hour Zero-based. Value from 0-23.
* @property {number} minute Zero-based. Value from 0-59.
* @property {number} second Zero-based. Value from 0-60 to allow for leap-seconds.
*/
export class PngLastModTimeEvent extends Event {
/** @param {PngLastModTime} lastModTime */
constructor(lastModTime) {
super(PngParseEventType.tIME);
/** @type {PngLastModTime} */
this.lastModTime = lastModTime;
}
}
/**
* @typedef PngChunk Internal use only.
* @property {number} length
@ -347,6 +367,16 @@ export class PngParser extends EventTarget {
return this;
}
/**
* Type-safe way to bind a listener for a PngLastModTime.
* @param {function(PngLastModTime): void} listener
* @returns {PngParser} for chaining
*/
onLastModTime(listener) {
super.addEventListener(PngParseEventType.tIME, listener);
return this;
}
/**
* Type-safe way to bind a listener for a PngPaletteEvent.
* @param {function(PngPaletteEvent): void} listener
@ -553,6 +583,20 @@ export class PngParser extends EventTarget {
this.dispatchEvent(new PngTextualDataEvent(textualData));
break;
// https://www.w3.org/TR/png-3/#11tIME
case 'tIME':
/** @type {PngLastModTime} */
const lastModTime = {
year: chStream.readNumber(2),
month: chStream.readNumber(1),
day: chStream.readNumber(1),
hour: chStream.readNumber(1),
minute: chStream.readNumber(1),
second: chStream.readNumber(1),
};
this.dispatchEvent(new PngLastModTimeEvent(lastModTime));
break;
// https://www.w3.org/TR/png-3/#11tRNS
case 'tRNS':
if (this.colorType === undefined) throw `tRNS before IHDR`;
@ -704,7 +748,10 @@ async function main() {
});
parser.onBackgroundColor(evt => {
// console.dir(evt.backgroundColor);
})
});
parser.onLastModTime(evt => {
console.dir(evt.lastModTime);
});
try {
await parser.start();
@ -714,4 +761,4 @@ async function main() {
}
}
// main();
// main();