Problem with loading a transparent image onto Labview FP proggrammatically

Question

Hi all,
I have a .png logo with transparent background, and I want to load it onto labview FP prorgrammatically. My problem is, if I load it programmatically (read image, display on image display), the background won't be transparent any more. But if I import it and paster it on labview FP manually, it looks OK.
I tried picture and it doesn't work.
Any idea? How to do it?
Thank you for any help.
Anne Zuo

Answer 1

You can sort of do it if you an image of the background as well (e.g. if you capture an image of the panel when the picture control is empty). As mentioned, the alpha channel is actually read from the PNG file, so what you need to do is average each component of each pixel with the data from the other image, but use the alpha information as a weight.
The code to do this is actually relatively simple (I already did it so I know, although I can't post it) - you need to get the image as a 2D array of U32 and then do a couple of Split Number operations, which will give you the RGB data as a set of 2D U8 arrays. You can then calculate the difference between each component of each pixel in the two pictures and multiply that by the ratio of the transparency (which either goes 0-100 or 0-255, I don't remember). You can then call Join Number to get the U32 array back, which you can wire into Draw Unflattened Pixmap.
You can also get rid of the picture control border by using a classic picture control or by right clicking the 3D frame and pressing the space bar a couple of times in the color dialog. This toggles between FG and BG colors and will allow you to color the frame transparent.
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