Generating a UIImage from a SCIChartSurface

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I’m try to generate a UIImage from a SCIChartSurface into a graphic context using the code below from a view that is not displayed on the screen. The image created is pure black, which indicates it did not draw. If I display the graph in a view on the devices screen, the graph draws correctly.

UIGraphicsBeginImageContextWithOptions(self.chart.bounds.size, NO, 0.0);
[self.chart drawViewHierarchyInRect:self.chart.bounds afterScreenUpdates:YES];
UIImage *chartImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

Are there any special steps that are needed to draw into a graphic context?

Version

2.5.0.2533

iOS SciChartSurface ios uiimage draw

Brian Smith asked 3 years ago

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Answers (3)

Best Answer

Update: In SciChart iOS v4 and above we now have a function for screenshots built in

Please see exportToUIImage and exportToUIImageWithRect in the SciChart iOS documentation.

Andrew Burnett-Thompson answered 2 months ago

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Hi Brian

We have a short code sample in our iOS Chart Documentation to export a screenshot of the chart to UIImage:

Because of using OpenGL as the main drawing framework, you might have some issues when capturing the screen with a SciChartSurface on it. But as a workaround here is a function for you to try:

-(UIImage*) screenshotFromView:(UIView*)view {
    CGSize size = CGSizeMake(view.frame.size.width, view.frame.size.height);
    UIGraphicsBeginImageContextWithOptions(size, false, UIScreen.mainScreen.scale);
    CGRect rec = CGRectMake(0, 0, view.frame.size.width,view.frame.size.height);
    [view drawViewHierarchyInRect:rec afterScreenUpdates:YES];
    UIImage * image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

Does this help?

Best regards,
Andrew

Andrew Burnett-Thompson answered 3 years ago

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This didn’t help.

I’m wondering if you are doing something, like drawing on a display link callback, that is not triggering if the chart is not added to an on screen view. Is this possible?

Brian Smith answered 3 years ago

- Nazar Rudnyk
- 3 years ago
Hello Brian, You are right, it’s drawing on a display link callback, and you are right, it’s need to be added into view on screen. Also, you might want to use exportToUIImage: method from SCIChartSurfaceProtocol – https://www.scichart.com/documentation/ios/v2.x/api/protocol_s_c_i_chart_surface_protocol-p.html#a513041bbe854d70ce1e4cf17f0d8b171, which is doing the code Andrew provided above. Best Regards, Nazar R.

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