in src/core/ccitt.js [509:844]
readNextChar() {
if (this.eof) {
return -1;
}
const refLine = this.refLine;
const codingLine = this.codingLine;
const columns = this.columns;
let refPos, blackPixels, bits, i;
if (this.outputBits === 0) {
if (this.rowsDone) {
this.eof = true;
}
if (this.eof) {
return -1;
}
this.err = false;
let code1, code2, code3;
if (this.nextLine2D) {
for (i = 0; codingLine[i] < columns; ++i) {
refLine[i] = codingLine[i];
}
refLine[i++] = columns;
refLine[i] = columns;
codingLine[0] = 0;
this.codingPos = 0;
refPos = 0;
blackPixels = 0;
while (codingLine[this.codingPos] < columns) {
code1 = this._getTwoDimCode();
switch (code1) {
case twoDimPass:
this._addPixels(refLine[refPos + 1], blackPixels);
if (refLine[refPos + 1] < columns) {
refPos += 2;
}
break;
case twoDimHoriz:
code1 = code2 = 0;
if (blackPixels) {
do {
code1 += code3 = this._getBlackCode();
} while (code3 >= 64);
do {
code2 += code3 = this._getWhiteCode();
} while (code3 >= 64);
} else {
do {
code1 += code3 = this._getWhiteCode();
} while (code3 >= 64);
do {
code2 += code3 = this._getBlackCode();
} while (code3 >= 64);
}
this._addPixels(codingLine[this.codingPos] + code1, blackPixels);
if (codingLine[this.codingPos] < columns) {
this._addPixels(
codingLine[this.codingPos] + code2,
blackPixels ^ 1
);
}
while (
refLine[refPos] <= codingLine[this.codingPos] &&
refLine[refPos] < columns
) {
refPos += 2;
}
break;
case twoDimVertR3:
this._addPixels(refLine[refPos] + 3, blackPixels);
blackPixels ^= 1;
if (codingLine[this.codingPos] < columns) {
++refPos;
while (
refLine[refPos] <= codingLine[this.codingPos] &&
refLine[refPos] < columns
) {
refPos += 2;
}
}
break;
case twoDimVertR2:
this._addPixels(refLine[refPos] + 2, blackPixels);
blackPixels ^= 1;
if (codingLine[this.codingPos] < columns) {
++refPos;
while (
refLine[refPos] <= codingLine[this.codingPos] &&
refLine[refPos] < columns
) {
refPos += 2;
}
}
break;
case twoDimVertR1:
this._addPixels(refLine[refPos] + 1, blackPixels);
blackPixels ^= 1;
if (codingLine[this.codingPos] < columns) {
++refPos;
while (
refLine[refPos] <= codingLine[this.codingPos] &&
refLine[refPos] < columns
) {
refPos += 2;
}
}
break;
case twoDimVert0:
this._addPixels(refLine[refPos], blackPixels);
blackPixels ^= 1;
if (codingLine[this.codingPos] < columns) {
++refPos;
while (
refLine[refPos] <= codingLine[this.codingPos] &&
refLine[refPos] < columns
) {
refPos += 2;
}
}
break;
case twoDimVertL3:
this._addPixelsNeg(refLine[refPos] - 3, blackPixels);
blackPixels ^= 1;
if (codingLine[this.codingPos] < columns) {
if (refPos > 0) {
--refPos;
} else {
++refPos;
}
while (
refLine[refPos] <= codingLine[this.codingPos] &&
refLine[refPos] < columns
) {
refPos += 2;
}
}
break;
case twoDimVertL2:
this._addPixelsNeg(refLine[refPos] - 2, blackPixels);
blackPixels ^= 1;
if (codingLine[this.codingPos] < columns) {
if (refPos > 0) {
--refPos;
} else {
++refPos;
}
while (
refLine[refPos] <= codingLine[this.codingPos] &&
refLine[refPos] < columns
) {
refPos += 2;
}
}
break;
case twoDimVertL1:
this._addPixelsNeg(refLine[refPos] - 1, blackPixels);
blackPixels ^= 1;
if (codingLine[this.codingPos] < columns) {
if (refPos > 0) {
--refPos;
} else {
++refPos;
}
while (
refLine[refPos] <= codingLine[this.codingPos] &&
refLine[refPos] < columns
) {
refPos += 2;
}
}
break;
case ccittEOF:
this._addPixels(columns, 0);
this.eof = true;
break;
default:
info("bad 2d code");
this._addPixels(columns, 0);
this.err = true;
}
}
} else {
codingLine[0] = 0;
this.codingPos = 0;
blackPixels = 0;
while (codingLine[this.codingPos] < columns) {
code1 = 0;
if (blackPixels) {
do {
code1 += code3 = this._getBlackCode();
} while (code3 >= 64);
} else {
do {
code1 += code3 = this._getWhiteCode();
} while (code3 >= 64);
}
this._addPixels(codingLine[this.codingPos] + code1, blackPixels);
blackPixels ^= 1;
}
}
let gotEOL = false;
if (this.byteAlign) {
this.inputBits &= ~7;
}
if (!this.eoblock && this.row === this.rows - 1) {
this.rowsDone = true;
} else {
code1 = this._lookBits(12);
if (this.eoline) {
while (code1 !== ccittEOF && code1 !== 1) {
this._eatBits(1);
code1 = this._lookBits(12);
}
} else {
while (code1 === 0) {
this._eatBits(1);
code1 = this._lookBits(12);
}
}
if (code1 === 1) {
this._eatBits(12);
gotEOL = true;
} else if (code1 === ccittEOF) {
this.eof = true;
}
}
if (!this.eof && this.encoding > 0 && !this.rowsDone) {
this.nextLine2D = !this._lookBits(1);
this._eatBits(1);
}
if (this.eoblock && gotEOL && this.byteAlign) {
code1 = this._lookBits(12);
if (code1 === 1) {
this._eatBits(12);
if (this.encoding > 0) {
this._lookBits(1);
this._eatBits(1);
}
if (this.encoding >= 0) {
for (i = 0; i < 4; ++i) {
code1 = this._lookBits(12);
if (code1 !== 1) {
info("bad rtc code: " + code1);
}
this._eatBits(12);
if (this.encoding > 0) {
this._lookBits(1);
this._eatBits(1);
}
}
}
this.eof = true;
}
} else if (this.err && this.eoline) {
while (true) {
code1 = this._lookBits(13);
if (code1 === ccittEOF) {
this.eof = true;
return -1;
}
if (code1 >> 1 === 1) {
break;
}
this._eatBits(1);
}
this._eatBits(12);
if (this.encoding > 0) {
this._eatBits(1);
this.nextLine2D = !(code1 & 1);
}
}
this.outputBits =
codingLine[0] > 0
? codingLine[(this.codingPos = 0)]
: codingLine[(this.codingPos = 1)];
this.row++;
}
let c;
if (this.outputBits >= 8) {
c = this.codingPos & 1 ? 0 : 0xff;
this.outputBits -= 8;
if (this.outputBits === 0 && codingLine[this.codingPos] < columns) {
this.codingPos++;
this.outputBits =
codingLine[this.codingPos] - codingLine[this.codingPos - 1];
}
} else {
bits = 8;
c = 0;
do {
if (typeof this.outputBits !== "number") {
throw new FormatError(
'Invalid /CCITTFaxDecode data, "outputBits" must be a number.'
);
}
if (this.outputBits > bits) {
c <<= bits;
if (!(this.codingPos & 1)) {
c |= 0xff >> (8 - bits);
}
this.outputBits -= bits;
bits = 0;
} else {
c <<= this.outputBits;
if (!(this.codingPos & 1)) {
c |= 0xff >> (8 - this.outputBits);
}
bits -= this.outputBits;
this.outputBits = 0;
if (codingLine[this.codingPos] < columns) {
this.codingPos++;
this.outputBits =
codingLine[this.codingPos] - codingLine[this.codingPos - 1];
} else if (bits > 0) {
c <<= bits;
bits = 0;
}
}
} while (bits);
}
if (this.black) {
c ^= 0xff;
}
return c;
}