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Use Calc to plot a line on an image of a chart?

asked 2016-09-28 11:56:20 +0100

David.Cheshire gravatar image

I have an image of a chart showing Young's modulus of iron plotted against temperature. There are several sets of data from different studies shown on the chart as curves and I would like to be able to overlay onto this a line that is a reasonable fit amongst these curves.

I tried to do this by generating a chart in Calc and setting the background to 100% transparent. I hoped that when I exported this to a .png file the transparency would remain so that I could overlay this chart on the image and the image would still be visible beneath the chart, but the exported .png chart has an opaque white background.

Any suggestions as to how I can use Calc to plot a line on an existing image of a chart would be welcomed.

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answered 2016-09-28 20:53:39 +0100

mark_t gravatar image

If you have the chart of curves as an xy plot then it would be better to just add a new series to that chart for the line, but I'm assuming that you don't have the original chart data to do this.

Instead of making the chart image transparent, set it as a background to your line chart and then the plot area of the line chart transparent as follows:-

Single click on the chart to select it, (not double click), click on the paint tin icon "Area" on the second row of the tool bar. In the Area dialog select the Bitmaps tab. Click on Import and select the png file.

On the area tab of the Area dialog, in Fill select Bitmap. Select the imported image from the list. Check Original under Size. Uncheck Tile. Uncheck Autofill.

Double click the chart to put it in edit mode.

Select "Chart Area" in drop down list. Click on "Format Selection" icon to the left of the drop down list. On the Transparency tab select Transparency and set to 100%.

Select "Chart" in drop down list. Click on "Format Selection" icon to the left of the drop down list. On the Transparency tab select Transparency and set to 100%.

Exit chart edit mode by clicking in the spreadsheet, then you should see the background image.

You will probably have quite a lot of formatting to modify to get a good appearance to the chart. Turning off grid lines, axis labels etc and aligning your chart to the background.

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Setting the image of the existing chart as the background of the Calc chart is exactly what I wanted, thanks!

David.Cheshire gravatar imageDavid.Cheshire ( 2016-10-06 13:01:18 +0100 )edit
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Asked: 2016-09-28 11:56:20 +0100

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Last updated: Sep 28 '16