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shaders/2d_cubism_norm_mul.gdshader

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+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: 2023 MizunagiKB <mizukb@live.jp>
+// GDCubism shader: Mul
+shader_type canvas_item;
+render_mode blend_premul_alpha, unshaded;
+
+uniform vec4 color_base : source_color;
+uniform vec4 color_screen : source_color;
+uniform vec4 color_multiply : source_color;
+uniform vec4 channel : source_color;
+uniform sampler2D tex_main : filter_linear_mipmap;
+
+varying vec4 modulate;
+
+void vertex() {
+	modulate = COLOR;
+}
+
+void fragment() {
+    vec4 color_tex = texture(tex_main, UV);
+    color_tex.rgb = color_tex.rgb * color_multiply.rgb;
+
+    // premul alpha
+    color_tex.rgb = (color_tex.rgb + color_screen.rgb) - (color_tex.rgb * color_screen.rgb);
+    vec4 color = color_tex * color_base * modulate;
+    COLOR = vec4(color.rgb * color.a, color.a);
+}