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Use the original array-data when parsing Type 0 (Sampled) Functions

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It seems just as easy to lookup the needed data in the original arrays, rather than having to first create (and allocate) nested arrays for that purpose.
This commit is contained in:
Jonas Jenwald 2026-04-04 14:03:11 +02:00
parent bc38b633ee
commit fa344c1852
1 changed files with 10 additions and 25 deletions
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35
src/core/function.js
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@ -155,22 +155,13 @@ class PDFFunction {
}
static constructSampled(factory, fn, dict) {
function toMultiArray(arr) {
const inputLength = arr.length;
const out = [];
let index = 0;
for (let i = 0; i < inputLength; i += 2) {
out[index++] = [arr[i], arr[i + 1]];
}
return out;
}
// See chapter 3, page 109 of the PDF reference
function interpolate(x, xmin, xmax, ymin, ymax) {
return ymin + (x - xmin) * ((ymax - ymin) / (xmax - xmin));
}
let domain = toNumberArray(dict.getArray("Domain"));
let range = toNumberArray(dict.getArray("Range"));
const domain = toNumberArray(dict.getArray("Domain"));
const range = toNumberArray(dict.getArray("Range"));
if (!domain || !range) {
throw new FormatError("No domain or range");
@ -179,9 +170,6 @@ class PDFFunction {
const inputSize = domain.length / 2;
const outputSize = range.length / 2;
domain = toMultiArray(domain);
range = toMultiArray(range);
const size = toNumberArray(dict.getArray("Size"));
const bps = dict.get("BitsPerSample");
const order = dict.get("Order") || 1;
@ -195,14 +183,11 @@ class PDFFunction {
if (!encode) {
encode = [];
for (let i = 0; i < inputSize; ++i) {
encode.push([0, size[i] - 1]);
encode.push(0, size[i] - 1);
}
} else {
encode = toMultiArray(encode);
}
let decode = toNumberArray(dict.getArray("Decode"));
decode = !decode ? range : toMultiArray(decode);
const decode = toNumberArray(dict.getArray("Decode")) || range;
const samples = this.getSampleArray(size, outputSize, bps, fn);
// const mask = 2 ** bps - 1;
@ -222,8 +207,8 @@ class PDFFunction {
// Map x_i to y_j for 0 <= i < m using the sampled function.
for (i = 0; i < inputSize; ++i) {
// x_i' = min(max(x_i, Domain_2i), Domain_2i+1)
const domain_2i = domain[i][0];
const domain_2i_1 = domain[i][1];
const domain_2i = domain[2 * i];
const domain_2i_1 = domain[2 * i + 1];
const xi = MathClamp(src[srcOffset + i], domain_2i, domain_2i_1);
// e_i = Interpolate(x_i', Domain_2i, Domain_2i+1,
@ -232,8 +217,8 @@ class PDFFunction {
xi,
domain_2i,
domain_2i_1,
encode[i][0],
encode[i][1]
encode[2 * i],
encode[2 * i + 1]
);
// e_i' = min(max(e_i, 0), Size_i - 1)
@ -269,10 +254,10 @@ class PDFFunction {
// r_j' = Interpolate(r_j, 0, 2^BitsPerSample - 1,
// Decode_2j, Decode_2j+1)
rj = interpolate(rj, 0, 1, decode[j][0], decode[j][1]);
rj = interpolate(rj, 0, 1, decode[2 * j], decode[2 * j + 1]);
// y_j = min(max(r_j, range_2j), range_2j+1)
dest[destOffset + j] = MathClamp(rj, range[j][0], range[j][1]);
dest[destOffset + j] = MathClamp(rj, range[2 * j], range[2 * j + 1]);
}
};
}