Don't apply dim to background color

Fixes #4161

addons/xterm-addon-canvas/src/CanvasAddon.ts

@@ -4,7 +4,7 @@
  */
 
 import { ICharacterJoinerService, ICharSizeService, ICoreBrowserService, IRenderService, ISelectionService, IThemeService } from 'browser/services/Services';
-import { IColorSet, ITerminal } from 'browser/Types';
+import { ITerminal } from 'browser/Types';
 import { CanvasRenderer } from './CanvasRenderer';
 import { IBufferService, ICoreService, IDecorationService, IOptionsService } from 'common/services/Services';
 import { ITerminalAddon, Terminal } from 'xterm';

addons/xterm-addon-canvas/src/TextRenderLayer.ts

@@ -188,12 +188,6 @@ export class TextRenderLayer extends BaseRenderLayer {
         nextFillStyle = this._themeService.colors.ansi[cell.getBgColor()].css;
       }
 
-      // Apply dim to the background, this is relatively slow as the CSS is re-parsed but dim is
-      // rarely used
-      if (nextFillStyle && cell.isDim()) {
-        nextFillStyle = color.multiplyOpacity(css.toColor(nextFillStyle), 0.5).css;
-      }
-
       // Get any decoration foreground/background overrides, this must be fetched before the early
       // exist but applied after inverse
       let isTop = false;