misskey/packages/frontend/src/utility/image-compositor-functions/pixelate.glsl

#version 300 es
precision mediump float;

/*
 * SPDX-FileCopyrightText: syuilo and misskey-project
 * SPDX-License-Identifier: AGPL-3.0-only
 */

const float PI = 3.141592653589793;
const float TWO_PI = 6.283185307179586;
const float HALF_PI = 1.5707963267948966;

in vec2 in_uv;
uniform sampler2D in_texture;
uniform vec2 in_resolution;
uniform vec2 u_offset;
uniform vec2 u_scale;
uniform bool u_ellipse;
uniform float u_angle;
uniform int u_samples;
uniform float u_strength;
out vec4 out_color;

// TODO: pixelateの中心を画像中心ではなく範囲の中心にする
// TODO: 画像のアスペクト比に関わらず各画素は正方形にする

void main() {
	if (u_strength <= 0.0) {
		out_color = texture(in_texture, in_uv);
		return;
	}

	float angle = -(u_angle * PI);
	vec2 centeredUv = in_uv - vec2(0.5, 0.5) - u_offset;
	vec2 rotatedUV = vec2(
		centeredUv.x * cos(angle) - centeredUv.y * sin(angle),
		centeredUv.x * sin(angle) + centeredUv.y * cos(angle)
	) + u_offset;

	bool isInside = false;
	if (u_ellipse) {
		vec2 norm = (rotatedUV - u_offset) / u_scale;
		isInside = dot(norm, norm) <= 1.0;
	} else {
		isInside = rotatedUV.x > u_offset.x - u_scale.x && rotatedUV.x < u_offset.x + u_scale.x && rotatedUV.y > u_offset.y - u_scale.y && rotatedUV.y < u_offset.y + u_scale.y;
	}

	if (!isInside) {
		out_color = texture(in_texture, in_uv);
		return;
	}

	float dx = u_strength / 1.0;
	float dy = u_strength / 1.0;
	vec2 new_uv = vec2(
		(dx * (floor((in_uv.x - 0.5 - (dx / 2.0)) / dx) + 0.5)),
		(dy * (floor((in_uv.y - 0.5 - (dy / 2.0)) / dy) + 0.5))
	) + vec2(0.5 + (dx / 2.0), 0.5 + (dy / 2.0));

	vec4 result = vec4(0.0);
	float totalSamples = 0.0;

	// TODO: より多くのサンプリング
	result += texture(in_texture, new_uv);
	totalSamples += 1.0;

	out_color = totalSamples > 0.0 ? result / totalSamples : texture(in_texture, in_uv);
}