how to draw a png on screen and move smoothly

[quantrpeter]

Hi. how to draw a png on screen and move it from left to right smoothly? i am using ST7735, thanks

[kdschlosser]

if you are using anything other than an I8080 or MIPI DSI connection to the screen it is going to be hard to get completely smooth. Depending on how much of the screen the image s going to be taking up is also going to really effect it as well.

In any of the cases you will want to decode the image to a raw RGB buffer this way there is not a constant decoding of the PNG data which will help a very large amount. This is going to consume a heck of a lot of memory when doing it. as an example...

if you are using a PNG image that has a size of 420x380 the total size of the buffer is going to end up being 420 * 380 * 3 = 478,800 bytes in size. so about 1/2 a meg of memory for the single image.

to do this preload you need to create a canvas widget and then create an image descriptor and also the buffer needs to be created that will fit the decoded image. You pass the buffer to the canvas widget. then you create a layer using the canvas widget and then call the render function for rendering an image to a layer. passing the layer and the image descriptor to that function. when it is done finalize the drawing and then you can pass the buffer directly to an lv image widget.

[quantrpeter]

thanks, let me try