A QGIS field calculator expression to generate pie charts to be inserted into an HTML frame in the composer

Svg_Pie_generator.py

#Korto19 2021

from qgis.core import *
from qgis.gui import *
import math

@qgsfunction(args='auto', group='Svg')
def svg_Pie(value, donut, pcol, flipper, legenda, feature, parent):
    """
    Genera un grafico a torta inseribile in una cornice HTML nel compositore di stampe
    <p style="color:Olive"><b>Sintassi</b></p>
    <p style="color:blue"><b>svg_Pie</b><mark style="color:black">(</mark>
    <mark style="color:red">array(values)</mark><mark style="color:black">,</mark>
    <mark style="color:red">donut</mark><mark style="color:black">,</mark>
    <mark style="color:red">array(colors)</mark><mark style="color:black">,</mark>
    <mark style="color:red">array(descriptions)</mark><mark style="color:black">,</mark>
    <mark style="color:red">legenda</mark><mark style="color:black">)</mark>
    <p style="color:Olive"><b>Argomenti</b></p>
    <p style="color:red"><b>array(values)</b><mark style="color:black"> - array percentuali </mark><br>
    <mark style="color:red"><b>donut </b><mark style="color:black"> - raggio del vuoto al centro [0-1]</mark><br>
    <mark style="color:red"><b>array(colors) </b><mark style="color:black"> - array colori</mark><br>
    <mark style="color:red"><b>array(descriptions) </b><mark style="color:black"> - array descrizioni</mark><br>
    <mark style="color:red"><b>legenda</b><mark style="color:black">
    <ul>
      <li>[-1] torta senza percentuali e legenda completa</li>
      <li>[ 0] torta con percentuali senza legenda</li>
      <li>[ 1] torta con percentuali  e legenda</mark><li>
    </ul>
    <h2><mark style="color:Olive"><strong>Example usage:</mark></strong></h2>
    <ul>
      <li><mark style="color:black"><strong>svg_Pie</strong>(array(.5,.1,.3),.8,array('red','cyan','gray'),array('uno','due','tre'),0)<li>
    </ul>  
    <mark style="color:black">
    <strong> La somma delle percentuali deve essere pari a 1 o inferiore</strong><br>
    <strong> Se la somma delle percentuali e' inferiore al 100% ci sara' un settore vuoto</strong><br>
    <strong> Elenco dei colori desiderati, se vuoto o in numero insufficiente saranno utilizzati quelli di default</strong><br>
    <strong> Elenco delle descrizioni, se vuoto o in numero insufficiente sara' utilizzato il carattere spazio</strong><br><br>
    Colori di default in ordine di utilizzo<br>
    Red, Aquamarine, Orange, Cyan, Yellow, Green, Grey, Beige, Gold, DarkKhaki, Royalblue, Fucsia<br>
    e' comunque possibile utilizzare qualsiasi colore CSS inserendone il nome
    """
    dcol =  ['red', 'Aquamarine', 'orange', 'cyan', 'yellow', 'green', 'grey', 'beige', 'Gold', 'DarkKhaki', 'royalblue', 'fucsia']
    
    #aggiunge colori mancanti
    if len(pcol) < len(value):
        for j in range (0, len(value)-len(pcol)+1):
            if dcol[j] not in pcol:
                pcol.append(dcol[j])
    
    #aggiunge vuoti se non ci son testi
    if len(flipper) < len(value):
        for j in range (0, len(value)-len(flipper)+1):
            flipper.append('')

    vc =  0.85
    vt = -0.81
    
    xi = '1'
    yi = '0'
    
    if legenda:
        riq = '''viewBox="-1.2 -1.2 4 4"'''
    else:
        riq = '''viewBox="-1.1 -1.1 2.2 2.2"'''
    
    svg_text = '''<svg width="100%" heigth="100%"'''+riq+'''" >
                <style>
                    #legend{
                        text-anchor: middle;
                        font-weight: bold;
                        font-size: .008em;
                        fill: purple;
                    }
                    text{
                        font-weight: light;
                        font-size: .006em;
                        font-family: Arial;
                        transform: rotate(90deg);
                    }
                    #perc{
                        fill: black;
                        font-weight: bold;
                        font-size: .006em;
                        font-family: Arial;
                        text-anchor: middle;
                    }
                    path{
                        stroke: white;
                        stroke-width: 0.01;
                    }
                </style>
                <g transform="translate(0,0) rotate(-90)">'''
        
    if sum(value[0:])>1:
        svg_text = 'Somma valori maggiore del 100%'
    else:
        for i in range (0, len(value)):
            pr = sum(value[0:i+1])
            vx = str(math.cos(2*3.14*pr))
            vy = str(math.sin(2*3.14*pr))
            if value[i] > 0.5:
                larc = '1'
            else:
                larc = '0'
            svg_text = svg_text + '''<path d= "M '''+ xi + ''' ''' + yi +''' A 1 1 0 ''' + larc + ''' 1 '''+ vx + ''' ''' + vy +''' L 0 0" fill="''' + pcol[i] + '''"/>'''
            xi = vx
            yi = vy
        
            if legenda == -1:
                svg_text = svg_text + '''<circle r="0.06" cx="'''+ str(vc) +'''" cy="1.4" fill="''' + pcol[i] + '''"/>
                                 <text x="1.5" y="'''+ str(vt) +'''" >'''+ "{:.2%}".format(value[i]) + " " + flipper[i] + '''</text>'''
                vc = vc - .2
                vt = vt + .2

            if legenda == 1:
                svg_text = svg_text + '''<circle r="0.06" cx="'''+ str(vc) +'''" cy="1.4" fill="''' + pcol[i] + '''"/>
                                 <text x="1.5" y="'''+ str(vt) +'''" >'''+ " " + flipper[i] + '''</text>'''
                vc = vc - .2
                vt = vt + .2
                
        if pr > 0.5:
            larc = '0'
        else:
            larc = '1'
        
        if donut:
            svg_text = svg_text + '''<circle r="''' + str(donut) + '''" cx="0" cy="0" fill="white" />'''
        
        if legenda:
            svg_text = svg_text + '''<text id="legend" x="1.9" y="-1">Legenda</text>'''
        
        #scrive percentuali entro torta
        if legenda >= 0:
            pr = 0
            for i in range (0, len(value)):
                pr = sum(value[0:i+1]) - value[i]/2
                vx = 0.8*math.cos(2*3.14*(pr-.25))
                vy = 0.8*math.sin(2*3.14*(pr-.25))
                svg_text = svg_text + '''<text id="perc" x="''' + str(vx) + '''" y="''' + str(vy) + '''">'''+"{:.2%}".format(value[i]) +'''</text>'''
        
        svg_text = svg_text + '''</g></svg>'''
    
    return svg_text

Alcuni esempi di utilizzo