Alpha issue with overlapping FastStepLineBitmapSeries

Question

Hello, when putting two series of type FastStepLineBitmapSeries on the same chart, the "bottom" series is hidden by the "top" series where they overlap, even though the interior brush of the top series has the alpha set to 50%. This makes it difficult to visualize the bottom series. Note: the top green series continuously alternates between 0 and 200.

Attached is a sample.

Some workarounds that I'm aware of:

- changing the order the series are added to the chart. In my particular application this is not a viable solution, the series need to be added in a pre-determined order.

- changing the series type to StepLineSeries. Not viable since I need the performance of the FastStepLineBitmapSeries.

Possible solution:

- Make an extension of the FastStepLineBitmapSeries and the FastStepLineBitmapSegment to modify how the lines are drawn in a way that allows the segment to "receive" other segments with alpha, allowing the segment to show through any overlapping segment. The advantage would be high performance together with alpha capability. The sample includes extensions in case you need them. I see the segment WritableBitmap is of type Pbgra32 which should handle transparency.

Is this possible or is there a better solution? Thanks.

Tom · Answer

Attachment.Attachment: SfChartTestSeriesAlpha_201dbc1e.rar

Devakumar Dhanapoosanam · Answer

Hi Tom, 
 
Greetings from Syncfusion. 
 
We have analyzed your query and tired the possibilities for achieving your requirement and facing some limitation for the FastBimapSeries since the series was rendered based on the series index order.  
 
We have also checked the Z Index of the series and it works only for the normal series.  
 
KB: https://www.syncfusion.com/kb/2681/how-to-set-the-z-index-to-the-series 
 
We need some more time to analyze the possible solution for your requirement using the FastStepLineBitMapSeries and we will update you the complete details on May 21, 2020. 
 
Regards, 
Devakumar D

Devakumar Dhanapoosanam · Answer

Hi Tom, 
 
We would like to let you know that currently the FastBitmapSeries will render based on the added series order and we don’t have the direct support for changing the series order of top position or the series transparency for the fastbitmap series. 
 
As you have mentioned earlier the possible workaround is adding the FastStepLineBitmapSeries on the series collection top. 
 
Incase if your requirement is like normal LineSeries we would like to suggest the FastLineSeries for better performance instead of the StepLineSeries. 
 
Please let us know if you need any further assistance on this. 
 
Regards, 
Devakumar D

Tom · Answer

Understood, thank you.

Hemalatha Marikumar · Answer

Hi Tom, 

 

Thanks for your update.

 

Please let us know if you need any further assistance.

 

Regards,
Hemalatha M.