From 39766e9f01965786c689716c7c42f190a608244a Mon Sep 17 00:00:00 2001
From: Sander Schobers <sander@schobers.eu>
Date: Wed, 20 May 2020 19:45:16 +0200
Subject: [PATCH] SDL surface is created from non-alpha-premultiplied colors.

---
 sdlui/image.go    | 10 ++++++++++
 sdlui/renderer.go |  3 ++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/sdlui/image.go b/sdlui/image.go
index 3e29bc0..669ed3b 100644
--- a/sdlui/image.go
+++ b/sdlui/image.go
@@ -5,6 +5,16 @@ import (
 	"image/draw"
 )
 
+func NRGBAImage(m image.Image) *image.NRGBA {
+	nrgba, ok := m.(*image.NRGBA)
+	if ok {
+		return nrgba
+	}
+	nrgba = image.NewNRGBA(m.Bounds())
+	draw.Draw(nrgba, nrgba.Bounds(), m, image.ZP, draw.Over)
+	return nrgba
+}
+
 func RGBAImage(m image.Image) *image.RGBA {
 	rgba, ok := m.(*image.RGBA)
 	if ok {
diff --git a/sdlui/renderer.go b/sdlui/renderer.go
index 9242502..7d4ef86 100644
--- a/sdlui/renderer.go
+++ b/sdlui/renderer.go
@@ -243,7 +243,7 @@ func (r *Renderer) createTexture(source ui.ImageSource, keepSource bool) (ui.Tex
 	if err != nil {
 		return nil, err
 	}
-	rgba := RGBAImage(m)
+	rgba := NRGBAImage(m)
 	width := int32(rgba.Bounds().Dx())
 	height := int32(rgba.Bounds().Dy())
 	surface, err := sdl.CreateRGBSurfaceWithFormatFrom(
@@ -257,6 +257,7 @@ func (r *Renderer) createTexture(source ui.ImageSource, keepSource bool) (ui.Tex
 	if err != nil {
 		return nil, err
 	}
+	texture.SetBlendMode(sdl.BLENDMODE_BLEND)
 	if keepSource {
 		return &TextureImageSource{&Texture{texture}, source}, nil
 	}