Set JPG background to white when omitBackground option is used (#700)

Author: kblok

lib/PuppeteerSharp.Tests/PageTests/ScreenshotTests.cs

@@ -236,6 +236,22 @@ await page.SetViewportAsync(new ViewPortOptions
             }
         }
 
+        [Fact]
+        public async Task ShouldRenderWhiteBackgroundOnJpegFile()
+        {
+            using (var page = await Context.NewPageAsync())
+            {
+                await page.SetViewportAsync(new ViewPortOptions { Width = 100, Height = 100 });
+                await page.GoToAsync(TestConstants.EmptyPage);
+                var screenshot = await page.ScreenshotDataAsync(new ScreenshotOptions
+                {
+                    OmitBackground = true,
+                    Type = ScreenshotType.Jpeg
+                });
+                Assert.True(ScreenshotHelper.PixelMatch("white.jpg", screenshot));
+            }
+        }
+
         [Fact]
         public async Task ShouldWorkWithOddClipSizeOnRetinaDisplays()
         {

lib/PuppeteerSharp.Tests/Screenshots/white.jpg

@@ -1729,7 +1729,7 @@ private async Task<string> PerformScreenshot(ScreenshotType type, ScreenshotOpti
                     }).ConfigureAwait(false);
                 }
 
-                if (options != null && options.OmitBackground)
+                if (options?.OmitBackground == true && type == ScreenshotType.Png)
                 {
                     await Client.SendAsync("Emulation.setDefaultBackgroundColorOverride", new
                     {
@@ -1774,7 +1774,7 @@ private async Task<string> PerformScreenshot(ScreenshotType type, ScreenshotOpti
 
         private Task ResetBackgroundColorAndViewport(ScreenshotOptions options)
         {
-            var omitBackgroundTask = options?.OmitBackground == true ?
+            var omitBackgroundTask = options?.OmitBackground == true && options.Type == ScreenshotType.Png ?
                 Client.SendAsync("Emulation.setDefaultBackgroundColorOverride") : Task.CompletedTask;
             var setViewPortTask = (options?.FullPage == true && Viewport != null) ?
                 SetViewportAsync(Viewport) : Task.CompletedTask;