PngParser: Add support for tIME chunk.

Author: codedread

image/parsers/png.js

@@ -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();

tests/image-parsers-png.spec.js

@@ -10,6 +10,7 @@ import { PngColorType, PngInterlaceMethod, PngParser } from '../image/parsers/pn
 /** @typedef {import('../image/parsers/png.js').PngImageGamma} PngImageGamma */
 /** @typedef {import('../image/parsers/png.js').PngImageHeader} PngImageHeader */
 /** @typedef {import('../image/parsers/png.js').PngIntlTextualData} PngIntlTextualData */
+/** @typedef {import('../image/parsers/png.js').PngLastModTime} PngLastModTime */
 /** @typedef {import('../image/parsers/png.js').PngPalette} PngPalette */
 /** @typedef {import('../image/parsers/png.js').PngSignificantBits} PngSignificantBits */
 /** @typedef {import('../image/parsers/png.js').PngTextualData} PngTextualData */
@@ -233,4 +234,18 @@ describe('bitjs.image.parsers.PngParser', () => {
       expect(bc.paletteIndex).equals(245);
     });
   });
+
+  it('extracts tIME', async () => {
+    /** @type {PngLastModTime} */
+    let lastModTime;
+    await getPngParser('tests/image-testfiles/cm9n0g04.png')
+        .onLastModTime(evt => { lastModTime = evt.lastModTime })
+        .start();
+    expect(lastModTime.year).equals(1999);
+    expect(lastModTime.month).equals(12);
+    expect(lastModTime.day).equals(31);
+    expect(lastModTime.hour).equals(23);
+    expect(lastModTime.minute).equals(59);
+    expect(lastModTime.second).equals(59);
+  });
 });