let OpenGL handle sRGB conversion

internal/render/render_world.go

@@ -126,7 +126,8 @@ func (r *WorldRenderer) Init(w *world.World) (err error) {
 	gl.GetFloatv(gl.MAX_TEXTURE_MAX_ANISOTROPY, &maxaf)
 
 	asset.InitWorldTextureAtlas()
-	r.texture = NewTextureRGBA(asset.WorldTextureAtlas.Image)
+	r.texture = NewTexture()
+	r.texture.UpdatesRGB(asset.WorldTextureAtlas.Image)
 	r.texture.GenerateMipMap()
 	gl.BindTexture(gl.TEXTURE_2D, r.texture.Handle())
 	gl.TexParameterf(gl.TEXTURE_2D, gl.TEXTURE_MAX_ANISOTROPY, maxaf)

internal/render/texture.go

@@ -127,6 +127,37 @@ func (t *Texture) UpdateRGBA(image *image.RGBA) {
 	t.updateFilters()
 }
 
+// UpdatesRGB updates the content of the texture with image in sRGB space.
+// It deletes existing mipmap, you need to generate it again.
+//
+// The internal data is converted from sRGB to linear space by OpenGL:
+//
+//   linear  =  sRGB/12.92              (if sRGB <= 0.04045)
+//            [(sRGB+0.055)/1.055]^2.4  (if sRGB > 0.04045)
+//
+// The Alpha component is not converted.
+func (t *Texture) UpdatesRGB(image *image.RGBA) {
+	// Restore current texture binding
+	defer gl.BindTexture(gl.TEXTURE_2D, curTextureBinding())
+
+	gl.BindTexture(gl.TEXTURE_2D, t.tex)
+	gl.TexImage2D(
+		gl.TEXTURE_2D,
+		0,
+		gl.SRGB_ALPHA,
+		int32(image.Rect.Size().X),
+		int32(image.Rect.Size().Y),
+		0,
+		gl.RGBA,
+		gl.UNSIGNED_BYTE,
+		gl.Ptr(image.Pix),
+	)
+	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST)
+
+	t.hasMipmap = false
+	t.updateFilters()
+}
+
 // GenerateMipMap generates mipmap for the texture.
 func (t *Texture) GenerateMipMap() {