It would not be too difficult to add this. The main pieces of the puzzle are:

1. Changing the min-filter to Linear so that scaling down retains some image quality.

   pixels/src/renderers.rs

   Line 38 in 94b8749

   min_filter: wgpu::FilterMode::Nearest,

2. Updating the resize constraints when creating the scaling matrix. The primary constraint is the max(1.0).floor() call here:

   pixels/src/renderers.rs

   Lines 233 to 237 in 94b8749

   	// Get smallest scale size
   	let scale = (screen_width / texture_width)
   	.min(screen_height / texture_height)
   	.max(1.0)
   	.floor();

There are probably some other things that also need to be updated along the way. But these are the most prominent in my mind.

I initially thought that using mipmapping would also help with quality and efficiency when scaling below the texture's native resolution. But it would add some complexity by requiring each mip level to be regenerated on every frame. That would definitely have a negative impact on efficiency. Mipmaps are beneficial for static textures, not dynamic textures.

@parasyte

Updating the resize constraints when creating the scaling matrix. The primary constraint is the max(1.0).floor() call here:

Can you tell how to update it? I copied the renderer.rs in the fill-window branch and removed .max(1.0) but it doesn't work

I copied the renderer.rs in the fill-window branch and removed .max(1.0) but it doesn't work

Did you also remove it in the default renderer? The default renderer is run first, followed by the custom renderer in the fill-window example.