node-red-contrib-pdf-hummus/nodes/lib/collection-state.js

Extract Text from a pdf using hummusjs

var _ = require('lodash');

function initTextState() {
    return  {
            charSpace:0,
            wordSpace:0,
            scale:100,
            leading:0,
            rise:0,
            font:null,
            tm: [1,0,0,1,0,0],
            tlm: [1,0,0,1,0,0],
            tmDirty:true,
            tlmDirty:true
        };
}

function cloneTextEnv(env) {
    return {
            charSpace:env.charSpace,
            wordSpace:env.wordSpace,
            scale:env.scale,
            leading:env.leading,
            rise:env.rise,
            font:env.font ? _.extend({},env.font):env.font,
            tm:env.tm.slice(),
            tlm:env.tlm.slice(),
            tmDirty:env.tmDirty,
            tlmDirty:env.tlmDirty
        }
}

function cloneGraphicEnv(env) {
    return {
        ctm:env.ctm.slice(),
        text:cloneTextEnv(env.text)
    }
}

function CollectionState() {
    this.graphicStateStack = [{
        ctm:[1,0,0,1,0,0],
        text:initTextState()
    }];
    this.inTextElement = false;
    this.textElementTextStack = null;
    this.texts = null;
}

CollectionState.prototype.pushGraphicState = function() {
    this.graphicStateStack.push(cloneGraphicEnv(this.graphicStateStack[this.graphicStateStack.length-1]));
    if(this.inTextElement) {
        this.textElementTextStack.push(cloneTextEnv(this.textElementTextStack[this.textElementTextStack.length-1]));
    }
}

CollectionState.prototype.popGraphicState = function() {
    if(this.graphicStateStack.length > 1)
        this.graphicStateStack.pop();
    if(this.inTextElement && this.textElementTextStack.length > 1)
        this.textElementTextStack.pop();
}

CollectionState.prototype.currentGraphicState = function() {
    return this.graphicStateStack[this.graphicStateStack.length-1];
}

CollectionState.prototype.currentTextState = function() {
    if(this.inTextElement) {
        return this.textElementTextStack[this.textElementTextStack.length-1];
    }
    else {
        return this.graphicStateStack[this.graphicStateStack.length-1].text;
    }
}

CollectionState.prototype.cloneCurrentTextState = function() {
    return cloneTextEnv(this.currentTextState());
}

CollectionState.prototype.startTextElement = function() {
    this.inTextElement = true;
    this.textElementTextStack = [cloneTextEnv(this.currentGraphicState().text)];
    this.texts = [];
}

CollectionState.prototype.endTextElement = function(placements) {

    // save text properties to persist after gone (some of them...)
    var latestTextState = this.cloneCurrentTextState();
    this.inTextElement = false;
    this.textElementTextStack = null;

    placements.push({
        type:'text',
        text: this.texts
    });    
    this.texts = null;

    // copy persisted data to top text state
    var persistingTextState =  this.currentTextState();
    ['charSpace','wordSpace','scale','leading','rise','font'].forEach((name)=> {
        persistingTextState[name] = latestTextState[name];
    });
}

module.exports = CollectionState;