feat(page): add omitBackground option for page.pdf method

docs/api.md

@@ -1825,6 +1825,7 @@ Page is guaranteed to have a main frame which persists during navigations.
     - `bottom` <[string]|[number]> Bottom margin, accepts values labeled with units.
     - `left` <[string]|[number]> Left margin, accepts values labeled with units.
   - `preferCSSPageSize` <[boolean]> Give any CSS `@page` size declared in the page priority over what is declared in `width` and `height` or `format` options. Defaults to `false`, which will scale the content to fit the paper size.
+  - `omitBackground` <[boolean]> Hides default white background and allows capturing screenshots with transparency. Defaults to `false`.
 - returns: <[Promise]<[Buffer]>> Promise which resolves with PDF buffer.
 
 > **NOTE** Generating a pdf is currently only supported in Chrome headless.

src/common/PDFOptions.ts

@@ -151,6 +151,11 @@ export interface PDFOptions {
    * @defaultValue the empty string, which means the PDF will not be written to disk.
    */
   path?: string;
+  /**
+   * Hides default white background and allows generating pdfs with transparency.
+   * @defaultValue false
+   */
+  omitBackground?: boolean;
 }
 
 /**

src/common/Page.ts

@@ -1271,6 +1271,22 @@ export class Page extends EventEmitter {
     this.emit(PageEmittedEvents.Dialog, dialog);
   }
 
+  /**
+   * Resets default white background
+   */
+  private async _resetDefaultBackgroundColor() {
+    await this._client.send('Emulation.setDefaultBackgroundColorOverride');
+  }
+
+  /**
+   * Hides default white background
+   */
+  private async _setTransparentBackgroundColor(): Promise<void> {
+    await this._client.send('Emulation.setDefaultBackgroundColorOverride', {
+      color: { r: 0, g: 0, b: 0, a: 0 },
+    });
+  }
+
   url(): string {
     return this.mainFrame().url();
   }
@@ -1720,18 +1736,18 @@ export class Page extends EventEmitter {
     }
     const shouldSetDefaultBackground =
       options.omitBackground && format === 'png';
-    if (shouldSetDefaultBackground)
-      await this._client.send('Emulation.setDefaultBackgroundColorOverride', {
-        color: { r: 0, g: 0, b: 0, a: 0 },
-      });
+    if (shouldSetDefaultBackground) {
+      await this._setTransparentBackgroundColor();
+    }
     const result = await this._client.send('Page.captureScreenshot', {
       format,
       quality: options.quality,
       clip,
       captureBeyondViewport: true,
     });
-    if (shouldSetDefaultBackground)
-      await this._client.send('Emulation.setDefaultBackgroundColorOverride');
+    if (shouldSetDefaultBackground) {
+      await this._resetDefaultBackgroundColor();
+    }
 
     if (options.fullPage && this._viewport)
       await this.setViewport(this._viewport);
@@ -1790,6 +1806,7 @@ export class Page extends EventEmitter {
       preferCSSPageSize = false,
       margin = {},
       path = null,
+      omitBackground = false,
     } = options;
 
     let paperWidth = 8.5;
@@ -1810,6 +1827,10 @@ export class Page extends EventEmitter {
     const marginBottom = convertPrintParameterToInches(margin.bottom) || 0;
     const marginRight = convertPrintParameterToInches(margin.right) || 0;
 
+    if (omitBackground) {
+      await this._setTransparentBackgroundColor();
+    }
+
     const result = await this._client.send('Page.printToPDF', {
       transferMode: 'ReturnAsStream',
       landscape,
@@ -1827,6 +1848,11 @@ export class Page extends EventEmitter {
       pageRanges,
       preferCSSPageSize,
     });
+
+    if (omitBackground) {
+      await this._resetDefaultBackgroundColor();
+    }
+
     return await helper.readProtocolStream(this._client, result.stream, path);
   }