Noob question about DrawImage - C++

[codeape]

Ok,

 

I load a texture:

mouse = Leadwerks::Texture::Load("Resources/Mousepointer/mouse.tex");

 

It is a png image that i have made a texture with that has DXT5 compression (the rest is Leadwerks default).

 

I then use it:

context->SetBlendMode(Leadwerks::Blend::Alpha);
context->SetColor(1.0, 1.0, 1.0, 0.8);
context->DrawImage(mouse, 300, 300, 16, 16);
context->SetBlendMode(Leadwerks::Blend::Solid);

 

Questions:

1. Why does the image color change to what ever color I set with SetColor? Why does the image not keep the color it had in its orignal png file? I do not say it is wrong I only wonder why.
   
2. Can I use DrawImage and keep all the colors in my image. If so are there any trade-offs?
   
3. Where can I read more?
   

[Guppy]

IIRC setting color to 0,0,0,0 will not tint the image

[gamecreator]

Pretty sure that turns it black. The DrawImage example uses this, just before drawing: context->SetColor(1,1,1);

[codeape]

IIRC setting color to 0,0,0,0 will not tint the image

 

The image went totaly black.

 

Pretty sure that turns it black. The DrawImage example uses this, just before drawing: context->SetColor(1,1,1);

 

Works , but why?

[whiterabbit]

context->SetColor(1,1,1);

 

Works , but why?

 

This is my basic explanation, hopefully I'm not too wrong.

 

When the image is drawn the color of each pixel is multiplied against the color set by context->SetColor.

 

So for example if pixel in the image is white (RGB = 255,255,255), and the context color is white (1,1,1), then they get multplied together.

R := 255 x 1.0 = 255
G := 255 x 1.0 = 255
B := 255 x 1.0 = 255

 

If the context color was black (0,0,0) everything would be multiplied by 0: 255x0=0

 

If the image pixel as red (255,0,0), and the context color was 50% grey (0.5,0.5,0.5) the final color would be a darker red (127,0,0)

R := 255 x 0.5 = 127
G :=   0 x 0.5 = 0
B :=   0 x 0.5 = 0

 

And the final example, the reason you would use this feature, is if your image was white you can use the context color to color the image. So, image is white (255,255,255) and say context color is orange (1,0.47,0)

R := 255 x 1.0  = 255
G := 255 x 0.47 = 120
B := 255 x 0.0  = 0

[codeape]

Thanks whiterabbit, gamecreator and Guppy.

 

So for example if pixel in the image is white (RGB = 255,255,255), and the context color is white (1,1,1), then they get multplied together.

 

Hmmm that explanation works for me

[codeape]

Whiterabbit i opened the drawimage.shader file today (I am learning GLSL) and I found this in the fragment shader:

 

void main(void)
{
fragData0 = drawcolor * texture(texture0,vTexCoords0);
}

 

This look like what you described above