Rotating Image around center with Context:SetRotation

[GorzenDev]

I'm trying to rotate a image around its center.
And since there is no rotation parameter for DrawImage(),
i thought i'd use Context:SetRotation() to achieve the result i need.
But i think i must be doing something wrong or do i need some math to translate the context everytime i rotate so it stays centered.?

Somehow a image always rotates around its topleft.
While a rectangle with proper rotation and translation CAN rotate around its center.

Can anybody help?

I have tried some different approaches as you can see and added rectangles with color to visualize.

            --cp is the center of the screen (the topleft position of (center - halfimgsize))
	    --newrot is controlled by the keyboard

	    --Red Rectangle
            context:SetRotation(newrot)
            gui:SetColor(1.0, 0.0, 0.0)
            gui:DrawImage(needle, cp.x + 128, cp.y, 256, 256)
            gui:DrawRect(cp.x + 128, cp.y, 256, 256, 1, 1)
            context:SetRotation(0.0)
            --
            --Green Rectangle
            context:SetRotation(newrot)
            context:SetTranslation(cp.x, cp.y + 128)
            gui:SetColor(0.0, 1.0, 0.0)
            gui:DrawImage(needle, -128, -128, 256, 256)
            gui:DrawRect(-128, -128, 256, 256, 1, 1)
            context:SetRotation(0.0)
            context:SetTranslation(0, 0)
            --
            --Blue Rectangle
            context:SetTranslation(cp.x, cp.y)
            context:SetRotation(newrot)
            gui:SetColor(0.0, 0.0, 1.0)
            gui:DrawImage(needle, -128, -128, 256, 256)
            gui:DrawRect(-128, -128, 256, 256, 1, 1)
            context:SetRotation(0.0)
            context:SetTranslation(0, 0)

 

 

[macklebee]

Try using this shader to rotate your images: drawimage_rotating.shader

Example script that shows usage:

window = Window:Create("draw rotating image",0,0,600,400,Window.Titlebar+Window.Center)
context = Context:Create(window)

imageshader = Shader:Load("Shaders/Drawing/drawimage_rotating.shader")
imageshader:SetVec2("pivotposition", Vec2(150.0, 37.5)) --center of image
angle = 0
image = Texture:Load("Materials/Developer/leadwerks.tex")

while window:KeyDown(Key.Escape)==false do
	if window:Closed() then break end	
	
	context:SetColor(1,.3,0)
	context:Clear()
	
	angle = angle +1
	
	defaultshader = context:GetShader()
	context:SetBlendMode(Blend.Alpha)
		
	--Draw Image
	context:SetColor(1, 1, 1)
	context:SetShader(imageshader)
	imageshader:SetFloat("angle", angle)
	context:DrawImage(image, 150, 150, 300, 75)
	
	context:SetShader(defaultshader)
	context:DrawText(string.format("FPS: %.2f",Time:UPS()), 0 ,10)
	context:SetBlendMode(Blend.Solid)
	context:Sync(true)
end

Video of this and other similar shaders:

 

[GorzenDev]

offcourse i should have thought about that ?‍♂️.
i whas so focused on simply rotating a image that i havent thought of using a shader.

thank you very much for your help, i whas about to give up and just use digits.