Weird PNG drawing??

Posted by Asmodeusbrooding on Wed 30 Aug 2023 11:58 PM — 3 posts, 9,967 views.

Asmodeusbrooding Wed 30 Aug 2023 11:58 PM #0

Hey Nick,

I've got some weird behavior here with loading and drawing a png...

You can run this code in immediate if you want...

Any idea what's going on?


-- Create miniwindow
win_id = "myMiniWindow"
WindowCreate(win_id, 0, 0, 100, 100, 1, 1, 0xFFFFFF)

-- Load image into miniwindow
WindowLoadImage(win_id, "building", "worlds\plugins\images\building.png")

-- Get window dimensions
local win_width, win_height = WindowInfo(win_id, 14), WindowInfo(win_id, 15)

-- Draw image to fill the entire window
WindowDrawImage(win_id, "building", 0, 0, win_width, win_height, miniwin.image_stretch)

-- Display the miniwindow
WindowShow(win_id, true)

and the image can be found here
https://imgur.com/F7Dq4X5

Seems odd....

On top of this, every time it draws it changes.. I used it on a map and every single time the map reloaded the image shifted slightly and if you redrew it many times it looked animated.

Is this caused by the png not being 8 bit or 24 bit or something? I converted a bmp to png on another conversion website and the image worked OK. I'd love to learn about why this one didn't work though..

Fiendish USA Global Moderator Thu 31 Aug 2023 10:33 AM #1

The image is 8 bit grey.

I wonder if either the calls to png_read_png from LoadPng and LoadPngMemory need to also include the PNG_TRANSFORM_GRAY_TO_RGB transform or the final bits per pixel needs to be made depth aware instead of choosing 24/32. The former seems safer.

See e.g.

https://github.com/nickgammon/mushclient/blob/5f1ca253cf6f44b65caeafd9f2ad7a4b87817c8e/Utilities.cpp#L3051-L3057

and

https://github.com/nickgammon/mushclient/blob/5f1ca253cf6f44b65caeafd9f2ad7a4b87817c8e/png/pngread.c#L1191-L1198

Nick Gammon Australia Forum Administrator Sat 02 Sep 2023 06:52 AM #2

That may well be the problem. If this is just one image try converting it to RGB with Gimp or some other program.