Adds support for the pHYs header (pngjs#383)

karvapallo · Mar 19, 2024 · d48ed28 · d48ed28
1 parent c565210
commit d48ed28
Show file tree

Hide file tree

Showing 5 changed files with 48 additions and 0 deletions.
diff --git a/lib/constants.js b/lib/constants.js
@@ -9,6 +9,7 @@ module.exports = {
   TYPE_PLTE: 0x504c5445,
   TYPE_tRNS: 0x74524e53, // eslint-disable-line camelcase
   TYPE_gAMA: 0x67414d41, // eslint-disable-line camelcase
+  TYPE_pHYs: 0x70485973, // eslint-disable-line camelcase
 
   // color-type bits
   COLORTYPE_GRAYSCALE: 0,

diff --git a/lib/parser-async.js b/lib/parser-async.js
@@ -16,6 +16,7 @@ let ParserAsync = (module.exports = function (options) {
     error: this._handleError.bind(this),
     metadata: this._handleMetaData.bind(this),
     gamma: this.emit.bind(this, "gamma"),
+    physical: this._handlePhysical.bind(this),
     palette: this._handlePalette.bind(this),
     transColor: this._handleTransColor.bind(this),
     finished: this._finished.bind(this),
@@ -113,6 +114,14 @@ ParserAsync.prototype._handleMetaData = function (metaData) {
   this._filter = new FilterAsync(this._bitmapInfo);
 };
 
+ParserAsync.prototype._handlePhysical = function (x, y, unit) {
+  this._metaData.physical = {
+    x: x,
+    y: y,
+    unit: unit,
+  };
+};
+
 ParserAsync.prototype._handleTransColor = function (transColor) {
   this._bitmapInfo.transColor = transColor;
 };

diff --git a/lib/parser-sync.js b/lib/parser-sync.js
@@ -46,6 +46,15 @@ module.exports = function (buffer, options) {
     gamma = _gamma_;
   }
 
+  let physical;
+  function handlePhysical(x, y, unit) {
+    physical = {
+      x: x,
+      y: y,
+      unit: unit,
+    };
+  }
+
   let inflateDataList = [];
   function handleInflateData(inflatedData) {
     inflateDataList.push(inflatedData);
@@ -58,6 +67,7 @@ module.exports = function (buffer, options) {
     error: handleError,
     metadata: handleMetaData,
     gamma: handleGamma,
+    physical: handlePhysical,
     palette: handlePalette,
     transColor: handleTransColor,
     inflateData: handleInflateData,
@@ -107,6 +117,9 @@ module.exports = function (buffer, options) {
 
   metaData.data = normalisedBitmapData;
   metaData.gamma = gamma || 0;
+  if (physical) {
+    metaData.physical = physical;
+  }
 
   return metaData;
 };
diff --git a/lib/parser.js b/lib/parser.js
@@ -22,11 +22,13 @@ let Parser = (module.exports = function (options, dependencies) {
   this._chunks[constants.TYPE_PLTE] = this._handlePLTE.bind(this);
   this._chunks[constants.TYPE_tRNS] = this._handleTRNS.bind(this);
   this._chunks[constants.TYPE_gAMA] = this._handleGAMA.bind(this);
+  this._chunks[constants.TYPE_pHYs] = this._handlePHYS.bind(this);
 
   this.read = dependencies.read;
   this.error = dependencies.error;
   this.metadata = dependencies.metadata;
   this.gamma = dependencies.gamma;
+  this.physical = dependencies.physical;
   this.transColor = dependencies.transColor;
   this.palette = dependencies.palette;
   this.parsed = dependencies.parsed;
@@ -253,6 +255,20 @@ Parser.prototype._parseGAMA = function (data) {
   this._handleChunkEnd();
 };
 
+Parser.prototype._handlePHYS = function (length) {
+  this.read(length, this._parsePHYS.bind(this));
+};
+Parser.prototype._parsePHYS = function (data) {
+  this._crc.write(data);
+  this.physical(
+    data.readUIntBE(0, 4),
+    data.readUIntBE(4, 4),
+    data.readUIntBE(8, 1)
+  );
+
+  this._handleChunkEnd();
+};
+
 Parser.prototype._handleIDAT = function (length) {
   if (!this._emittedHeadersFinished) {
     this._emittedHeadersFinished = true;

diff --git a/test/png-parse-spec.js b/test/png-parse-spec.js
@@ -377,6 +377,15 @@ test("should set alpha=true in metadata for images with tRNS chunk", function (t
     });
 });
 
+test("should set the pHYs header in metadata for images with a pHYs chunk", function (t) {
+  fs.createReadStream(path.join(__dirname, "in", "cdfn2c08.png"))
+    .pipe(new PNG())
+    .on("metadata", function (metadata) {
+      t.ok(metadata.physical, "Image should have a pHys header");
+      t.end();
+    });
+});
+
 test("Should parse with low highWaterMark", function (t) {
   fs.createReadStream(path.join(__dirname, "in", "tbbn0g04.png"), {
     highWaterMark: 2,