mirrors/CyberChef
1
0
Fork 0
mirror of https://github.com/gchq/CyberChef.git synced 2025-05-10 00:05:11 -04:00
Code Issues Projects Releases Packages Wiki Activity Actions 1

separate output and presentation

Browse source
This commit is contained in:
Andy Wang 2020-04-02 01:37:38 +01:00
parent e156f620b9
commit 345c169ac7
1 changed files with 31 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

38
src/core/operations/ExtractQuantisationTables.mjs
View file

@ -24,23 +24,23 @@ class ExtractQuantisationTables extends Operation {
this.description = "Extracts quantisation tables embedded in a JPEG image."; this.description = "Extracts quantisation tables embedded in a JPEG image.";
this.infoURL = "https://en.wikipedia.org/wiki/Quantization_(image_processing)"; this.infoURL = "https://en.wikipedia.org/wiki/Quantization_(image_processing)";
this.inputType = "ArrayBuffer"; this.inputType = "ArrayBuffer";
this.outputType = "string"; this.outputType = "json";
this.presentType = "string";
this.args = []; this.args = [];
} }
/** /**
* @param {ArrayBuffer} input * @param {ArrayBuffer} input
* @param {Object[]} args * @param {Object[]} args
* @returns {string} * @returns {json}
*/ */
run(input, args) { run(input, args) {
const image = new Uint8Array(input); const image = new Uint8Array(input);
// maximally 4 tables are allowed in a JPEG file
let ptr = indexOfMarker(image, 0xD8); let ptr = indexOfMarker(image, 0xD8);
if (ptr === -1) throw new OperationError("Malformed image file: Start of Image not found"); if (ptr === -1) throw new OperationError("Malformed image file: Start of Image not found");
let ret = ""; const ret = {};
do { do {
const dqtIndex = indexOfMarker(image, 0xDB, ptr); const dqtIndex = indexOfMarker(image, 0xDB, ptr);
@ -57,9 +57,13 @@ class ExtractQuantisationTables extends Operation {
if (tableId >= 4) throw new OperationError(`Invalid table identifier ${tableId} at table definition beginning at ${dqtIndex}`); if (tableId >= 4) throw new OperationError(`Invalid table identifier ${tableId} at table definition beginning at ${dqtIndex}`);
const table = parseQTable(image.slice(dqtIndex + 5, dqtIndex + 5 + tableLength), doublePrecision); const table = parseQTable(image.slice(dqtIndex + 5, dqtIndex + 5 + tableLength), doublePrecision);
ret += `Quantisation table at position ${dqtIndex}. ID ${tableId}, ${(doublePrecision? "16":"8")}-bit precision:\n`; // there may be two sets of quantisation tables, one in the embedded thumbnail and one for the main image
ret += this.prettifyMatrix(table); // we extract both sets so there may be tables with duplicate identifiers
ret += "\n"; ret[dqtIndex] = {
id: tableId,
precision: doublePrecision? 16:8,
table: table
};
ptr = dqtIndex + 5 + tableLength + 1; ptr = dqtIndex + 5 + tableLength + 1;
} while (ptr < image.length); } while (ptr < image.length);
@ -67,6 +71,26 @@ class ExtractQuantisationTables extends Operation {
return ret; return ret;
} }
/**
* Pretty print the tables with description
*
* @param {json} tables
* @param {Object[]} args
* @returns {string}
*/
present(tables, args) {
let ret = "";
for (const dqtIndex in tables) {
const tableInfo = tables[dqtIndex];
ret += `Quantisation table at position ${dqtIndex}. ID ${tableInfo.id}, ${tableInfo.precision}-bit precision:\n`;
ret += this.prettifyMatrix(tableInfo.table);
ret += "\n";
}
return ret;
}
/** /**
* @param {number[][]} mat * @param {number[][]} mat
* @returns {string} * @returns {string}