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[Editor] Guess font size and color from the AS of FreeText annotations
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@calixteman
calixteman committed Jun 5, 2023
1 parent 77fb683 commit ba8c996
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Showing 3 changed files with 238 additions and 5 deletions.
16 changes: 11 additions & 5 deletions src/core/annotation.js
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Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,7 @@ import {
createDefaultAppearance,
FakeUnicodeFont,
getPdfColor,
parseAppearanceStream,
parseDefaultAppearance,
} from "./default_appearance.js";
import { Dict, isName, Name, Ref, RefSet } from "./primitives.js";
Expand Down Expand Up @@ -3545,20 +3546,25 @@ class FreeTextAnnotation extends MarkupAnnotation {
const { xref } = params;
this.data.annotationType = AnnotationType.FREETEXT;
this.setDefaultAppearance(params);
if (!this.appearance && this._isOffscreenCanvasSupported) {
if (this.appearance) {
const { fontColor, fontSize } = parseAppearanceStream(this.appearance);
this.data.defaultAppearanceData.fontColor = fontColor;
this.data.defaultAppearanceData.fontSize = fontSize || 10;
} else if (this._isOffscreenCanvasSupported) {
const strokeAlpha = params.dict.get("CA");
const fakeUnicodeFont = new FakeUnicodeFont(xref, "sans-serif");
const fontData = this.data.defaultAppearanceData;
this.data.defaultAppearanceData.fontSize ||= 10;
const { fontColor, fontSize } = this.data.defaultAppearanceData;
this.appearance = fakeUnicodeFont.createAppearance(
this._contents.str,
this.rectangle,
this.rotation,
fontData.fontSize || 10,
fontData.fontColor,
fontSize,
fontColor,
strokeAlpha
);
this._streams.push(this.appearance, FakeUnicodeFont.toUnicodeStream);
} else if (!this._isOffscreenCanvasSupported) {
} else {
warn(
"FreeTextAnnotation: OffscreenCanvas is not supported, annotation may not render correctly."
);
Expand Down
87 changes: 87 additions & 0 deletions src/core/default_appearance.js
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Original file line number Diff line number Diff line change
Expand Up @@ -87,6 +87,92 @@ function parseDefaultAppearance(str) {
return new DefaultAppearanceEvaluator(str).parse();
}

class AppearanceStreamEvaluator extends EvaluatorPreprocessor {
constructor(stream) {
super(stream);
this.stream = stream;
}

parse() {
const operation = {
fn: 0,
args: [],
};
let result = {
scaleFactor: 1,
fontSize: 0,
fontName: "",
fontColor: /* black = */ new Uint8ClampedArray(3),
};
let breakLoop = false;
const stack = [];

try {
while (true) {
operation.args.length = 0; // Ensure that `args` it's always reset.

if (breakLoop || !this.read(operation)) {
break;
}
const { fn, args } = operation;

switch (fn | 0) {
case OPS.save:
stack.push({
scaleFactor: result.scaleFactor,
fontSize: result.fontSize,
fontName: result.fontName,
fontColor: result.fontColor.slice(),
});
break;
case OPS.restore:
result = stack.pop() || result;
break;
case OPS.setTextMatrix:
result.scaleFactor *= Math.hypot(args[0], args[1]);
break;
case OPS.setFont:
const [fontName, fontSize] = args;
if (fontName instanceof Name) {
result.fontName = fontName.name;
}
if (typeof fontSize === "number" && fontSize > 0) {
result.fontSize = fontSize * result.scaleFactor;
}
break;
case OPS.setFillRGBColor:
ColorSpace.singletons.rgb.getRgbItem(args, 0, result.fontColor, 0);
break;
case OPS.setFillGray:
ColorSpace.singletons.gray.getRgbItem(args, 0, result.fontColor, 0);
break;
case OPS.setFillColorSpace:
ColorSpace.singletons.cmyk.getRgbItem(args, 0, result.fontColor, 0);
break;
case OPS.showText:
case OPS.showSpacedText:
case OPS.nextLineShowText:
case OPS.nextLineSetSpacingShowText:
breakLoop = true;
break;
}
}
} catch (reason) {
warn(`parseAppearanceStream - ignoring errors: "${reason}".`);
}
this.stream.reset();
delete result.scaleFactor;

return result;
}
}

// Parse appearance stream to extract font and color information.
// It returns the font properties used to render the first text object.
function parseAppearanceStream(stream) {
return new AppearanceStreamEvaluator(stream).parse();
}

function getPdfColor(color, isFill) {
if (color[0] === color[1] && color[1] === color[2]) {
const gray = color[0] / 255;
Expand Down Expand Up @@ -368,5 +454,6 @@ export {
createDefaultAppearance,
FakeUnicodeFont,
getPdfColor,
parseAppearanceStream,
parseDefaultAppearance,
};
140 changes: 140 additions & 0 deletions test/unit/default_appearance_spec.js
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Original file line number Diff line number Diff line change
Expand Up @@ -15,8 +15,10 @@

import {
createDefaultAppearance,
parseAppearanceStream,
parseDefaultAppearance,
} from "../../src/core/default_appearance.js";
import { StringStream } from "../../src/core/stream.js";

describe("Default appearance", function () {
describe("parseDefaultAppearance and createDefaultAppearance", function () {
Expand Down Expand Up @@ -50,4 +52,142 @@ describe("Default appearance", function () {
});
});
});

describe("parseAppearanceStream", () => {
it("should parse a FreeText (from Acrobat) appearance", () => {
const appearance = new StringStream(`
0 w
46.5 621.0552 156.389 18.969 re
n
q
1 0 0 1 0 0 cm
46.5 621.0552 156.389 18.969 re
W
n
0 g
1 w
BT
/Helv 14 Tf
0.419998 0.850006 0.160004 rg
46.5 626.77 Td
(Hello ) Tj
35.793 0 Td
(World ) Tj
40.448 0 Td
(from ) Tj
31.89 0 Td
(Acrobat) Tj
ET
Q`);
const result = {
fontSize: 14,
fontName: "Helv",
fontColor: new Uint8ClampedArray([107, 217, 41]),
};
expect(parseAppearanceStream(appearance)).toEqual(result);
expect(appearance.pos).toEqual(0);
});

it("should parse a FreeText (from Firefox) appearance", () => {
const appearance = new StringStream(`
q
0 0 203.7 28.3 re W n
BT
1 0 0 1 0 34.6 Tm 0 Tc 0.93 0.17 0.44 rg
/Helv 18 Tf
0 -24.3 Td (Hello World From Firefox) Tj
ET
Q`);
const result = {
fontSize: 18,
fontName: "Helv",
fontColor: new Uint8ClampedArray([237, 43, 112]),
};
expect(parseAppearanceStream(appearance)).toEqual(result);
expect(appearance.pos).toEqual(0);
});

it("should parse a FreeText (from Preview) appearance", () => {
const appearance = new StringStream(`
q Q q 2.128482 2.128482 247.84 26 re W n /Cs1 cs 0.52799 0.3071 0.99498 sc
q 1 0 0 -1 -108.3364 459.8485 cm BT 22.00539 0 0 -22.00539 110.5449 452.72
Tm /TT1 1 Tf [ (H) -0.2 (e) -0.2 (l) -0.2 (l) -0.2 (o) -0.2 ( ) 0.2 (W) 17.7
(o) -0.2 (rl) -0.2 (d) -0.2 ( ) 0.2 (f) 0.2 (ro) -0.2 (m ) 0.2 (Pre) -0.2
(vi) -0.2 (e) -0.2 (w) ] TJ ET Q Q`);
const result = {
fontSize: 22.00539,
fontName: "TT1",
fontColor: new Uint8ClampedArray([0, 0, 0]),
};
expect(parseAppearanceStream(appearance)).toEqual(result);
expect(appearance.pos).toEqual(0);
});

it("should parse a FreeText (from Edge) appearance", () => {
const appearance = new StringStream(`
q
0 0 292.5 18.75 re W n
BT
0 Tc
0.0627451 0.486275 0.0627451 rg
0 3.8175 Td
/Helv 16.5 Tf
(Hello World from Edge without Acrobat) Tj
ET
Q`);
const result = {
fontSize: 16.5,
fontName: "Helv",
fontColor: new Uint8ClampedArray([16, 124, 16]),
};
expect(parseAppearanceStream(appearance)).toEqual(result);
expect(appearance.pos).toEqual(0);
});

it("should parse a FreeText (from Foxit) appearance", () => {
const appearance = new StringStream(`
q
/Tx BMC
0 -22.333 197.667 22.333 re
W
n
BT
0.584314 0.247059 0.235294 rg
0 -18.1 Td
/FXF0 20 Tf
(Hello World from Foxit) Tj
ET
EMC
Q`);
const result = {
fontSize: 20,
fontName: "FXF0",
fontColor: new Uint8ClampedArray([149, 63, 60]),
};
expect(parseAppearanceStream(appearance)).toEqual(result);
expect(appearance.pos).toEqual(0);
});

it("should parse a FreeText (from Okular) appearance", () => {
const appearance = new StringStream(`
q
0.00 0.00 172.65 41.46 re W n
0.00000 0.33333 0.49804 rg
BT 1 0 0 1 0.00 41.46 Tm
/Invalid_font 18.00 Tf
0.00 -18.00 Td
(Hello World from) Tj
/Invalid_font 18.00 Tf
0.00 -18.00 Td
(Okular) Tj
ET Q`);
const result = {
fontSize: 18,
fontName: "Invalid_font",
fontColor: new Uint8ClampedArray([0, 85, 127]),
};
expect(parseAppearanceStream(appearance)).toEqual(result);
expect(appearance.pos).toEqual(0);
});
});
});

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