Change transparency of color in chart

[Conny Söderholm]

Hi,

I am trying to change the transparency of a Chart.

I tried to pass an ARGB to the ColorChoice, but that does not work.

I also tried to create a new class to pass the color, but I am limited by what colorchoice accepts. Any suggestions on how to solve it?

https://openpyxl.readthedocs.io/en/stable/api/openpyxl.drawing.colors.html

Best,

Conny

[Charlie Clark]

What does your code look like? I don't think this is possible yet
because openpyxl does not expose all of the chart structure (that's all
7 layers of hell) in a way that you work with it.

Charlie

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[Conny Söderholm]

Ideally, I would like to pass the Alpha to the green color for example  "4D228b22" but this gives an error upon opening.

I have tried creating a separate ColorChoice object as well but I cannot pass a modified color object to it.

This works for setting a green color. Other example after this code.

from openpyxl import Workbook
from openpyxl.chart import AreaChart, Reference

import datetime, random

output_filename = "OpenPyXL_Area_Charts.xlsx"
output_wb = Workbook()
output_ws = output_wb.active

# Create some dates
dates = [datetime.date(2020, x, 1) for x in range(1,10,2)]

# Create som values for first and seconds bars
bars1 = [random.randint(10,50) for _ in range(5)]
bars2 = [random.randint(10,50) for _ in range(5)]

# Write the values to the sheet
for row in zip(dates,bars1, bars2):
    output_ws.append(row)

#Create the References
date_series = Reference(output_ws, min_col=1, min_row=1, max_col=1, max_row=5)
area1_series = Reference(output_ws, min_col=2, min_row=1, max_col=2, max_row=5)
area2_series = Reference(output_ws, min_col=3, min_row=1, max_col=3, max_row=5)

# Add Area Chart
area_chart = AreaChart()
area_chart.add_data(area1_series)

# Set the color of area1_series to green
green_color = "228b22"

a1_series = area_chart.series[0]
a1_series.graphicalProperties.line.solidFill = green_color
a1_series.graphicalProperties.solidFill = green_color

area_chart.add_data(area2_series)
area_chart.set_categories(date_series)
area_chart.title = "Bar Chart colors"
area_chart.x_axis.title = "Dates"
area_chart.y_axis.title = "Values"

output_ws.add_chart(area_chart, "A16")
output_wb.save(output_filename)

################################

But I would like to do like this

# Create green color
green_color = Color("228b22")

green_color.rgb =  "4D228b22"

a1_series = area_chart.series[0]
a1_series.graphicalProperties.line.solidFill = ColorChoice(srgbClr=green_color)
a1_series.graphicalProperties.solidFill = ColorChoice(srgbClr=green_color)

srgbClr needs to be passed as a string, but then I cannot pass a color with Alpha channel to change transparency.

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Conny Söderholm about.me/connysoderholm

[Charlie Clark]

On 18 Mar 2021, at 15:10, Conny Söderholm wrote:

> But I would like to do like this
> # Create green color
> green_color = Color("228b22")
> green_color.rgb = "4D228b22"
>
> a1_series = area_chart.series[0]
> a1_series.graphicalProperties.line.solidFill =
> ColorChoice(srgbClr=green_color)
> a1_series.graphicalProperties.solidFill =
> ColorChoice(srgbClr=green_color)
>
> srgbClr needs to be passed as a string, but then I cannot pass a color
> with
> Alpha channel to change transparency.

Hm, looks like you're diving deep into DrawingML. Support for this in
openpyxl is neither complete nor error-free. Basically, I did enough to
support charts and some other things but you can tell by the lack of
tests that this not sufficient.

I assume you're already reverse engineering, right? Well, you should be
able to create the correct object from some XML and just pass it in:
it's often much easier than creating the code imperatively and probably
one of openpyxl's most powerful hacks.