Create Actor from pixel data instead of image file

[aviks]

Create Actor from pixel data instead of image file

[jwortmann]

I've gotten it to work!

There were a few pitfalls that I had to figure out:

• the SDL function expects the pixel data as an array of UInt32 numbers, so the 8-bit color values for each channel first need to be combined into a single UInt32 for each pixel
• (I think that) the pixel array which is passed as an argument needs to be stored in a permanent variable, so that the garbage collector won't free the corresponding memory which is referenced from the SDL function
• depth is the combined bit-depth of all channels, i.e. here it should be set to 32
• excerpt from the SDL3 docs at https://wiki.libsdl.org/SDL3/SDL_CreateSurfaceFrom#remarks

  Pitch is the offset in bytes from one row of pixels to the next, e.g. width*4 for SDL_PIXELFORMAT_RGBA8888.

So with this my code example looks as follows:

using SimpleDirectMediaLayer

images = Vector{UInt32}[]

function MyImageActor(image; kv...)
    height, width = size(image)
    depth = 32  # 8 bit per channel
    pitch = 4 * width
    format = SimpleDirectMediaLayer.LibSDL2.SDL_PIXELFORMAT_RGBA8888

    pixels = UInt32[]
    sizehint!(pixels, height * width)

    for pixel in 255 * image'
        push!(pixels, UInt32(red(pixel)) << 24 | UInt32(green(pixel)) << 16 | UInt32(blue(pixel)) << 8 | UInt32(alpha(pixel)))
    end

    push!(images, pixels)  # prevent memory of the pixel array being freed by garbage collector
    sf = SimpleDirectMediaLayer.LibSDL2.SDL_CreateRGBSurfaceWithFormatFrom(pixels, width, height, depth, pitch, format)
    sf == C_NULL && error("surface is NULL")
    a = GameZero.Actor("", sf, Rect(0, 0, width, height), [1.0, 1.0], 0, 255, Dict{Symbol,Any}())
    for (k, v) in kv
        setproperty!(a, k, v)
    end
    return a
end

Probably there is potential for improvements in the code, but it seems to work so far. I still think it would be useful to have something like this built-in and managed directly by GameZero, so perhaps this issue can stay open as a feature request.