Saving GL data to file

How-to Discussions
1

Hi,

I’m trying to save GL data to an image file.

I have this:

	public void SaveUno() {
		int size = (int) ActualSize[0] * (int) ActualSize[1] * 4;
		var data = new byte[size];
		int w = (int) ActualSize[0];
		int h = (int) ActualSize[1];
		OpenGL.GL.ReadPixels(0,0, w, h, GLPixelFormat.Rgba, GLPixelType.UnsignedByte, data);
		SaveImage(data, size, w, h, "/Users/bolav/Image.png");
	}

	public void SaveImage(byte[] data, int size, int w, int h, string fn)
	@{
		uBase::Buffer *buf = uBase::Buffer::CopyFrom(data, size);

		uImage::Bitmap *bmp = new uImage::Bitmap(w, h, uImage::FormatRGBA_8_8_8_8_Int, buf, 0, 0);
		uBase::String tfn = "/Users/bolav/Image.png";
		uImage::Png::Save(tfn, bmp);
	@}

But I have some issues.

The data array does not seem to get the actual data, so I’m doing something wrong there.

How can I convert from uString to uBase::String?

The Png save crashes, so I’m certain that there are some errors with creating the bitmap or something around there.

2

ActualSize is in points, not pixels… that could be the issue?

3

Open.GL.ReadPixels returns 255 for all bytes, so I think I have to attach it or something to get actual data. Also uImage::Png::Save just crashes.

4

What element are you trying to read data from?

MapViews are known to not work, becuase of a DRM mechanism in the OS.

5

Also, what framebuffer have you attached?

Png::Save will crash with your above code because you are interpreting points as pixels (i.e. your buffer is too small)

6

You might also want to do GL.PixelStore(GLPixelStoreParameter.PackAlignment, 1); to avoid OpenGL computing padding at the end of each scanline.

7

I’ve created a Control that you can draw on. I’m trying to dump it to an image. I’ve not connected any framebuffer, the whole save code is what you see. I understand that this is the reason it’s not working, and was hoping for a full example.

On CMake the error from Png::Save is Unsupported PNG Format: FormatRGBA_8_8_8_8_Int. It might be the same error on the other platforms.

8

Hello!

I’ve been trying to save two pictures that get imported from camera roll as one PNG. So i have a canvas (DockPanel) with two movable pictures in it. These need to be saved together as one PNG.

So, how can i use the framebuffer class to generate a PNG file for me? Have you figured this out yet Bjørn-Olav?

Thanks so much!

9

@bolav: The Png::Save issue is because we require FormatRGBA_8_8_8_8_UInt_Normalize instead of FormatRGBA_8_8_8_8_Int in the png-saver.

10

Erik helped me solve this, and created these great components!

11

Great components!! I’m impressed by that Uno level.
A month ago we had to go native because Fuse did not have a component like this