Scale up bitmap size to fit in 300 dpi image to accomodate small fonts docs

services/printing/DEPS

@@ -1,5 +1,6 @@
 include_rules = [
   "+pdf",
+  "+printing",
   "+third_party/skia/include",
   "+ui/gfx/geometry",
 ]

services/printing/pdf_to_bitmap_converter.cc

@@ -11,6 +11,7 @@
 #include "base/logging.h"
 #include "base/memory/shared_memory_mapping.h"
 #include "pdf/pdf.h"
+#include "printing/units.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/gfx/geometry/size_conversions.h"
 
@@ -49,6 +50,8 @@ void PdfToBitmapConverter::GetBitmap(
   }
   auto pdf_buffer = pdf_map.GetMemoryAsSpan<const uint8_t>();
 
+  // Get the original size of the PDF page in points. Each point is 1/72 inch
+  // per chrome_pdf::CalculatePosition and printing::kPointsPerInch.
   std::optional<gfx::SizeF> page_size =
       chrome_pdf::GetPDFPageSizeByIndex(pdf_buffer, page_index);
   if (!page_size.has_value()) {
@@ -56,8 +59,14 @@ void PdfToBitmapConverter::GetBitmap(
     std::move(callback).Run(SkBitmap());
     return;
   }
-  gfx::Size size = gfx::ToCeiledSize(*page_size);
+  // Scale up the page size from 72 dpi to 300 dpi
+  gfx::SizeF size_300dpi = gfx::ScaleSize(
+      page_size.value(),
+      static_cast<float>(printing::kDefaultPdfDpi) / printing::kPointsPerInch);
+  gfx::Size size = gfx::ToCeiledSize(size_300dpi);
 
+  // Allocate a bitmap with the scaled up size so it can fit in later rendered
+  // 300 dpi PDF page image.
   SkBitmap bitmap;
   const SkImageInfo info = SkImageInfo::Make(
       size.width(), size.height(), kBGRA_8888_SkColorType, kOpaque_SkAlphaType);
@@ -75,9 +84,11 @@ void PdfToBitmapConverter::GetBitmap(
       .use_color = true,
       .render_device_type = chrome_pdf::RenderDeviceType::kDisplay,
   };
-  if (!chrome_pdf::RenderPDFPageToBitmap(pdf_buffer, page_index,
-                                         bitmap.getPixels(), size,
-                                         gfx::Size(300, 300), options)) {
+  // Render the PDF page to a bitmap with 300 dpi with scaled up size.
+  if (!chrome_pdf::RenderPDFPageToBitmap(
+          pdf_buffer, page_index, bitmap.getPixels(), size,
+          gfx::Size(printing::kDefaultPdfDpi, printing::kDefaultPdfDpi),
+          options)) {
     DLOG(ERROR) << "Failed to render PDF buffer as bitmap image";
     std::move(callback).Run(SkBitmap());
     return;

services/printing/sources.gni

@@ -8,4 +8,7 @@ brave_services_printing_sources = [
   "//brave/services/printing/pdf_to_bitmap_converter.h",
 ]
 
-brave_services_printing_deps = [ "//components/discardable_memory/client" ]
+brave_services_printing_deps = [
+  "//components/discardable_memory/client",
+  "//printing:printing_base",
+]

test/data/leo/long_canvas.html

@@ -26,14 +26,25 @@
       var context = canvas.getContext('2d');
       context.font = '30px Arial';
       context.fillText('This is the way.', 50, 100);
+
       // leave page 2 empty
+
       canvas = document.getElementById('page3');
       context = canvas.getContext('2d');
       context.font = '30px Arial';
       context.fillText('I have spoken.', 50, 100);
+
+      // smaller text with higher DPI
       canvas = document.getElementById('page4');
+      const dpr = 2;
+      const rect = canvas.getBoundingClientRect();
+      canvas.width = rect.width * dpr;
+      canvas.height = rect.height * dpr;
+      canvas.style.width = `${rect.width}px`;
+      canvas.style.height = `${rect.height}px`;
       context = canvas.getContext('2d');
-      context.font = '30px Arial';
+      context.scale(dpr, dpr);
+      context.font = '15px Arial';
       context.fillText('Wherever I Go, He Goes.', 50, 100);
     </script>
 </body>