Lv_img_set_zoom with filesystem

[embeddedt]

Unfortunately, image transformations are not supported with images loaded from the filesystem at this time. See this post:

How to Scale/Rotate image from flash memory?

Unfortunately, zoom and rotate requires the whole image. The reason: imagine that lvgl draws x=10, y=20 pixel of the image. The image is rotated and zoom, so for (10;20) e.g. (87,33) should be drawn. But if only y = 20 line is available lvgl can’t get (87, 33). A corner case is when rotate = 90° so the line becomes columns. When lvgl draws the pixels of a line (x, x+1, x+2, …) different lines will be required for each pixel (y, y+1, y+2).