SDL: examples/save-rendering-to-bitmaps: Dump alpha channel.

SDL Commits
1 
From 8fe1d7faec7e910d9bb0f88ca6e95afd75e582d3 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Wed, 20 May 2026 00:40:25 -0400
Subject: [PATCH] examples/save-rendering-to-bitmaps: Dump alpha channel.

examples/renderer/20-blending triggered this: the renderer's framebuffer has
an alpha channel, even if the window itself doesn't, so we ended up with some
weird rendering in the onmouseover.webp when I rebuilt it.
---
 examples/save-rendering-to-bitmaps.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/examples/save-rendering-to-bitmaps.h b/examples/save-rendering-to-bitmaps.h
index bf3eab8df791d..e75bf238060e1 100644
--- a/examples/save-rendering-to-bitmaps.h
+++ b/examples/save-rendering-to-bitmaps.h
@@ -32,6 +32,11 @@ static bool SAVERENDERING_SDL_RenderPresent(SDL_Renderer *renderer)
     if (!surface) {
         SDL_LogError(SDL_LOG_CATEGORY_RENDER, "Failed to read pixels for frame #%u! (%s)", framenum, SDL_GetError());
     } else {
+        SDL_Surface *cvt = SDL_ConvertSurface(surface, SDL_PIXELFORMAT_RGBX32);
+        if (cvt) {
+            SDL_DestroySurface(surface);
+            surface = cvt;
+        }
         char fname[64];
         SDL_snprintf(fname, sizeof (fname), "frame%05u.png", framenum);
         if (!SDL_SavePNG(surface, fname)) {