osu/osu.Game/Graphics/Backgrounds/Background.cs

123 lines
4.7 KiB
C#

// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.
using System;
using System.Diagnostics;
using osu.Framework.Allocation;
using osu.Framework.Graphics;
using osu.Framework.Graphics.Containers;
using osu.Framework.Graphics.Sprites;
using osu.Framework.Graphics.Textures;
using osu.Framework.Graphics.Transforms;
using osuTK;
namespace osu.Game.Graphics.Backgrounds
{
/// <summary>
/// A background which offers blurring via a <see cref="BufferedContainer"/> on demand.
/// </summary>
public class Background : CompositeDrawable, IEquatable<Background>
{
public readonly Sprite Sprite;
private readonly string textureName;
private BufferedContainer bufferedContainer;
public Background(string textureName = @"")
{
this.textureName = textureName;
RelativeSizeAxes = Axes.Both;
AddInternal(Sprite = new Sprite
{
RelativeSizeAxes = Axes.Both,
Anchor = Anchor.Centre,
Origin = Anchor.Centre,
FillMode = FillMode.Fill,
});
}
[BackgroundDependencyLoader]
private void load(LargeTextureStore textures)
{
if (!string.IsNullOrEmpty(textureName))
Sprite.Texture = textures.Get(textureName);
}
public Vector2 BlurSigma => Vector2.Divide(bufferedContainer?.BlurSigma ?? Vector2.Zero, blurScale);
/// <summary>
/// Smoothly adjusts <see cref="IBufferedContainer.BlurSigma"/> over time.
/// </summary>
/// <returns>A <see cref="TransformSequence{T}"/> to which further transforms can be added.</returns>
public void BlurTo(Vector2 newBlurSigma, double duration = 0, Easing easing = Easing.None)
{
if (bufferedContainer == null && newBlurSigma != Vector2.Zero)
{
RemoveInternal(Sprite);
AddInternal(bufferedContainer = new BufferedContainer(cachedFrameBuffer: true)
{
RelativeSizeAxes = Axes.Both,
RedrawOnScale = false,
Child = Sprite
});
}
if (bufferedContainer != null)
transformBlurSigma(newBlurSigma, duration, easing);
}
private void transformBlurSigma(Vector2 newBlurSigma, double duration, Easing easing)
=> this.TransformTo(nameof(blurSigma), newBlurSigma, duration, easing);
private Vector2 blurSigmaBacking = Vector2.Zero;
private Vector2 blurScale = Vector2.One;
private Vector2 blurSigma
{
get => blurSigmaBacking;
set
{
Debug.Assert(bufferedContainer != null);
blurSigmaBacking = value;
blurScale = new Vector2(calculateBlurDownscale(value.X), calculateBlurDownscale(value.Y));
bufferedContainer.FrameBufferScale = blurScale;
bufferedContainer.BlurSigma = value * blurScale; // If the image is scaled down, the blur radius also needs to be reduced to cover the same pixel block.
}
}
/// <summary>
/// Determines a factor to downscale the background based on a given blur sigma, in order to reduce the computational complexity of blurs.
/// </summary>
/// <param name="sigma">The blur sigma.</param>
/// <returns>The scale-down factor.</returns>
private float calculateBlurDownscale(float sigma)
{
// If we're blurring within one pixel, scaling down will always result in an undesirable loss of quality.
// The algorithm below would also cause this value to go above 1, which is likewise undesirable.
if (sigma <= 1)
return 1;
// A good value is one where the loss in quality as a result of downscaling the image is not easily perceivable.
// The constants here have been experimentally chosen to yield nice transitions by approximating a log curve through the points {{ 1, 1 }, { 4, 0.75 }, { 16, 0.5 }, { 32, 0.25 }}.
float scale = -0.18f * MathF.Log(0.004f * sigma);
// To reduce shimmering, the scaling transitions are limited to happen only in increments of 0.2.
return MathF.Round(scale / 0.2f, MidpointRounding.AwayFromZero) * 0.2f;
}
public virtual bool Equals(Background other)
{
if (ReferenceEquals(null, other)) return false;
if (ReferenceEquals(this, other)) return true;
return other.GetType() == GetType()
&& other.textureName == textureName;
}
}
}