How to Render PDF with Foxit PDF SDK C++

PDF rendering is realized through the Foxit renderer, a graphics engine that is used to render a page to a bitmap or platform graphics device. Foxit PDF SDK provides APIs to set rendering options/flags. As an example, you can set up a flag to decide whether to render form fields and signature, or whether to draw image anti-aliasing and path anti-aliasing. To render, you can use the following APIs:

To render page and annotations, first use function Renderer::SetRenderContentFlags to decide whether to render page and annotation both or not, and then use function Renderer::StartRender to do the rendering. Function Renderer::StartQuickRender can also be used to render page but only for thumbnail purpose.
To render a single annotation, use function Renderer::RenderAnnot.
To render on a bitmap, use function Renderer::StartRenderBitmap.
To render a reflowed page, use function Renderer::StartRenderReflowPage.

Widget annotation is always associated with form field and form control in Foxit PDF SDK. For how to render widget annotations, here is a recommended flow:

After loading a PDF page, first render the page and all annotations in this page (including widget annotations).
Then, if use pdf::interform::Filler object to fill the form, the function pdf::interform::Filler::Render should be used to render the focused form control instead of the function Renderer::RenderAnnot.

Example:

How to render a page to a bitmap

#include "include/common/fs_common.h"#include "include/pdf/fs_pdfdoc.h"#include "include/pdf/fs_pdfpage.h"#include "include/common/fs_render.h"
using namespace foxit;using namespace common;using namespace pdf;using namespace foxit::common;
// Assuming PDFPage page has been loaded and parsed.int width = static_cast(page.GetWidth());int height = static_cast(page.GetHeight());Matrix matrix = page.GetDisplayMatrix(0, 0, width, height, page.GetRotation());

// Prepare a bitmap for rendering.Bitmap bitmap(width, height, Bitmap::e_DIBArgb, NULL, 0);bitmap.FillRect(0xFFFFFFFF, NULL);
// Render page.Renderer render(bitmap, false);render.StartRender(page, matrix, NULL);...

How to render page and annotation

#include "include/common/fs_common.h"#include "include/pdf/fs_pdfdoc.h"#include "include/pdf/fs_pdfpage.h"#include "include/common/fs_render.h"
using namespace foxit;using namespace common;using namespace pdf;using namespace foxit::common;
// Assuming PDFPage page has been loaded and parsed.int width = static_cast(page.GetWidth());int height = static_cast(page.GetHeight());Matrix matrix = page.GetDisplayMatrix(0, 0, width, height, page.GetRotation());

// Prepare a bitmap for rendering.
Bitmap bitmap(width, height, Bitmap::e_DIBArgb, NULL, 0);
bitmap.FillRect(0xFFFFFFFF, NULL);

Renderer render(bitmap, false);
uint32 dwRenderFlag = Renderer::e_RenderAnnot | Renderer::e_RenderPage;
render.SetRenderContentFlags(dwRenderFlag);
render.StartRender(page, matrix, NULL);
...