Qt顯示pdf系列4——封裝pdfium庫為動態庫,顯示pdf
承接上篇,pdfium的lib檔案是已經編譯出來了,理論上已經可以開始直接用了,官方提供的測試demo中基本上介紹了用法的整套流程,你可以選擇匯出一頁頁的(圖片)檔案,也可以直接取出Buffer丟給支援圖形庫去渲染。
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但是需要注意的是,他在實際使用中依舊有很多不便:
1、我們能夠編譯出來的只有vs2015或以上版本的lib,如果我們需要在別的ide中引用,那麼就可能不行。
2、編譯出來的lib一共24個,所以確定要在專案中,光pdf庫就引用這麼多個嗎= =。
解決方式:基於這些lib的基礎上,再包一層,把他編譯成動態庫,介面用純C語言,不僅簡潔,而且理論上說是跨平臺的。
關於動態庫,只簡單說幾句,不瞭解可以自己查:靜態連結庫(.lib)cpp裡所有程式碼被被編譯成2進位制檔案,使用時直接會連線到你的專案中,而動態連結庫,裡面是你專案的程式碼,也不會編譯進你的程式中。
開發環境:windows7+vs2015
一、新建專案:
開啟vs2015,新建一個c++的win32專案,當然,你也可以直接新建成空專案,然後在設定裡手動修改輸出方式為dll。這裡我的專案叫pdf
二、封裝pdfium庫:
1、把上篇編譯出來的pdfium庫的lib和標頭檔案整理好,並新增到剛才新建的專案中去:
2、在專案中新建PdfManager.h,PdfManager.cpp。開始寫程式碼:
PdfManager.h:
#ifndef _PDF_MANAGER_H_
#define _PDF_MANAGER_H_
//filename是檔名,需要唯一,dat是開啟的pdf的內容(可以用fstream開啟,以二進位制形式),length是pdf長度
extern "C" _declspec(dllexport) bool __stdcall PDFMANAGER_Loadpdf(const char* filename, char* dat, int length); //載入pdf(即載入已經開啟的pdf)
//filename是檔名,關閉該pdf
extern "C" _declspec(dllexport) bool __stdcall PDFMANAGER_Closepdf(const char* filename); //關閉pdf
//filename是檔名,關閉該pdf,page是需要顯示頁數,width是寬,height是高,size是當前頁的大小,outBmp是是否匯出bmp檔案,返回該頁buffer
extern "C" _declspec(dllexport) char* __stdcall PDFMANAGER_LoadPage(const char* filename, int page, float& width, float& height, int& size, bool OutBmp);//載入頁面
//filename是檔名,關閉該頁面,開啟後需要關閉,否則會記憶體洩漏
extern "C" _declspec(dllexport) void __stdcall PDFMANAGER_ClosePage(const char* filename, int page); //關閉頁面
//獲取總頁數
extern "C" _declspec(dllexport) int __stdcall PDFMANAGER_GetPageCount(const char* filename);
//獲取下一頁該渲染的頁
extern "C" _declspec(dllexport) int __stdcall PDFMANAGER_GetCurrentPage(const char* filename);
#endif
PdfManager.cpp:
#include "PdfManager.h"
#include "fpdfview.h"
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <memory>
#include <map>
#include <sstream>
#include <string>
#include <utility>
#include <vector>
#include "fpdf_dataavail.h"
#include "fpdf_edit.h"
#include "fpdf_ext.h"
#include "fpdf_formfill.h"
#include "fpdf_text.h"
#include <functional>
#include <fstream>
enum OutputFormat
{
OUTPUT_STR,
OUTPUT_BMP,
};
struct Options
{
Options() :pages(false), output_format(OUTPUT_BMP) {}
bool pages; //是否指定範圍
OutputFormat output_format;
int first_page = 0; //起始頁數
int last_page = 0; //終止頁數
int currentpage = 0; //要列印的頁面
float width = 0; //目標寬度
float height = 0; //目標高度
};
FPDF_BOOL Is_Data_Avail(FX_FILEAVAIL* avail, size_t offset, size_t size)
{
return true;
}
class PDFManager
{
static std::string WriteBmp(int num,
const void* buffer,
int stride,
int width,
int height)
{
if (stride < 0 || width < 0 || height < 0)
return false;
if (height > 0 && width > INT_MAX / height)
return false;
int out_len = stride * height;
if (out_len > INT_MAX / 3)
return "";
char filename[256];
snprintf(filename, sizeof(filename), "%d.bmp", num);
FILE* fp = fopen(filename, "wb");
if (!fp)
return "";
BITMAPINFO bmi = {};
bmi.bmiHeader.biSize = sizeof(bmi) - sizeof(RGBQUAD);
bmi.bmiHeader.biWidth = width;
bmi.bmiHeader.biHeight = -height; // top-down image
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = 32;
bmi.bmiHeader.biCompression = BI_RGB;
bmi.bmiHeader.biSizeImage = 0;
BITMAPFILEHEADER file_header = {};
file_header.bfType = 0x4d42;
file_header.bfSize = sizeof(file_header) + bmi.bmiHeader.biSize + out_len;
file_header.bfOffBits = file_header.bfSize - out_len;
fwrite(&file_header, sizeof(file_header), 1, fp);
fwrite(&bmi, bmi.bmiHeader.biSize, 1, fp);
fwrite(buffer, out_len, 1, fp);
fclose(fp);
return std::string(filename);
}
struct FPDF_FORMFILLINFO_PDFiumTest : public FPDF_FORMFILLINFO
{
// Hold a map of the currently loaded pages in order to avoid them
// to get loaded twice.
std::map<int, FPDF_PAGE> loaded_pages;
// Hold a pointer of FPDF_FORMHANDLE so that PDFium app hooks can
// make use of it.
FPDF_FORMHANDLE form_handle;
};
struct AvailDeleter
{
inline void operator()(FPDF_AVAIL avail) const
{
FPDFAvail_Destroy(avail);
}
};
static FPDF_FORMFILLINFO_PDFiumTest* ToPDFiumTestFormFillInfo(FPDF_FORMFILLINFO* form_fill_info)
{
return static_cast<FPDF_FORMFILLINFO_PDFiumTest*>(form_fill_info);
}
FPDF_PAGE GetPageForIndex(FPDF_FORMFILLINFO* param,
FPDF_DOCUMENT& doc,
int index)
{
FPDF_FORMFILLINFO_PDFiumTest* form_fill_info =
ToPDFiumTestFormFillInfo(param);
auto& loaded_pages = form_fill_info->loaded_pages;
auto iter = loaded_pages.find(index);
if (iter != loaded_pages.end())
return iter->second;
FPDF_PAGE page = FPDF_LoadPage(doc, index);
if (!page)
return nullptr;
FPDF_FORMHANDLE& form_handle = form_fill_info->form_handle;
FORM_OnAfterLoadPage(page, form_handle);
FORM_DoPageAAction(page, form_handle, FPDFPAGE_AACTION_OPEN);
loaded_pages[index] = page;
return page;
}
char* RenderPage(FPDF_DOCUMENT& doc,
FPDF_FORMFILLINFO_PDFiumTest& form_fill_info
, float& width, float& height,
const Options& options,
int& size)
{
FPDF_PAGE page = GetPageForIndex(&form_fill_info, doc, options.currentpage);
if (!page)
{
return nullptr;
}
FPDF_TEXTPAGE text_page = FPDFText_LoadPage(page);
double scale = 1.0;
int widthdraw = static_cast<int>(FPDF_GetPageWidth(page) * scale);
int heightdraw = static_cast<int>(FPDF_GetPageHeight(page) * scale);
if (options.width > 0 && options.height > 0)
{
if (options.width > options.height)
{
double scalewidth = (double)options.height / (double)heightdraw;
heightdraw = options.height;
widthdraw = scalewidth * widthdraw;
}
else
{
double scaleheight = (double)options.width / (double)widthdraw;
widthdraw = options.width;
heightdraw = scaleheight * heightdraw;
}
}
//else
//{
// widthdraw = static_cast<int>(FPDF_GetPageWidth(page) * scale);
// heightdraw = static_cast<int>(FPDF_GetPageHeight(page) * scale);
//}
int alpha = FPDFPage_HasTransparency(page) ? 1 : 0;
FPDF_BITMAP bitmap = FPDFBitmap_Create(widthdraw, heightdraw, alpha);
const char* buffer = nullptr;
char* rtnBuffer = nullptr;
int out_len = 0;
if (bitmap)
{
FPDF_DWORD fill_color = alpha ? 0x00000000 : 0xFFFFFFFF;
FPDFBitmap_FillRect(bitmap, 0, 0, widthdraw, heightdraw, fill_color);
FPDF_RenderPageBitmap(bitmap, page, 0, 0, widthdraw, heightdraw, 0, FPDF_ANNOT | FPDF_REVERSE_BYTE_ORDER);
//FPDF_FFLDraw(form, bitmap, page, 0, 0, width, height, 0, FPDF_ANNOT | FPDF_REVERSE_BYTE_ORDER);
int stride = FPDFBitmap_GetStride(bitmap);
int strheight = FPDFBitmap_GetHeight(bitmap);
buffer = reinterpret_cast<const char*>(FPDFBitmap_GetBuffer(bitmap));
//開闢新記憶體
size = stride * strheight;
rtnBuffer = new char[size];
memset(rtnBuffer, 0, size);
memcpy(rtnBuffer, buffer, size);
width = FPDFBitmap_GetWidth(bitmap);
height = FPDFBitmap_GetHeight(bitmap);
Pages_.insert(std::make_pair(options.currentpage, rtnBuffer));
switch (options.output_format)
{
case OUTPUT_BMP:
WriteBmp(options.currentpage, buffer, stride, widthdraw, heightdraw);
break;
default:
break;
}
FPDFBitmap_Destroy(bitmap);
}
/*else
fprintf(stderr, "Page was too large to be rendered.\n");*/
form_fill_info.loaded_pages.erase(options.currentpage);
/*FORM_DoPageAAction(page, form, FPDFPAGE_AACTION_CLOSE);
FORM_OnBeforeClosePage(page, form);*/
FPDFText_ClosePage(text_page);
FPDF_ClosePage(page);
return rtnBuffer;
}
class TestLoader
{
public:
TestLoader(const char* buff, size_t len)
{
m_pBuf = new char[len];
memcpy(m_pBuf, buff, len);
m_Len = len;
}
~TestLoader()
{
delete[]m_pBuf;
}
static int GetBlock(void* param,
unsigned long pos,
unsigned char* pBuf,
unsigned long size)
{
TestLoader* pLoader = static_cast<TestLoader*>(param);
if (pos + size < pos || pos + size > pLoader->m_Len)
return 0;
memcpy(pBuf, pLoader->m_pBuf + pos, size);
return 1;
}
private:
char* m_pBuf;
size_t m_Len;
};
void RenderPdf(const char* pBuf, size_t len, const Options& options)
{
memset(&platform_callbacks_, '\0', sizeof(platform_callbacks_));
platform_callbacks_.version = 3;
form_callbacks_.version = 1;
form_callbacks_.m_pJsPlatform = &platform_callbacks_;
Loader_ = std::move(std::unique_ptr<TestLoader>(new TestLoader(pBuf, len)));
File_access_ = std::make_unique<FPDF_FILEACCESS>();
memset(File_access_.get(), '\0', sizeof(File_access_.get()));
File_access_->m_FileLen = static_cast<unsigned long>(len);
File_access_->m_GetBlock = TestLoader::GetBlock;
File_access_->m_Param = Loader_.get();
memset(&File_avail_, '\0', sizeof(File_avail_));
File_avail_.version = 1;
File_avail_.IsDataAvail = Is_Data_Avail;
memset(&Hints_, '\0', sizeof(Hints_));
Hints_.version = 1;
int nRet = PDF_DATA_NOTAVAIL;
Pdf_avail_ = FPDFAvail_Create(&File_avail_, File_access_.get());
std::unique_ptr<void, PDFManager::AvailDeleter> scoped_pdf_avail_deleter(Pdf_avail_);
if (FPDFAvail_IsLinearized(Pdf_avail_) == PDF_LINEARIZED)
{
this->PdfDoc_ = FPDFAvail_GetDocument(Pdf_avail_, nullptr);
if (this->PdfDoc_)
{
while (nRet == PDF_DATA_NOTAVAIL)
nRet = FPDFAvail_IsDocAvail(Pdf_avail_, &Hints_);
if (nRet == PDF_DATA_ERROR)
{
fprintf(stderr, "Unknown error in checking if doc was available.\n");
FPDF_CloseDocument(this->PdfDoc_);
return;
}
nRet = FPDFAvail_IsFormAvail(Pdf_avail_, &Hints_);
if (nRet == PDF_FORM_ERROR || nRet == PDF_FORM_NOTAVAIL)
{
fprintf(stderr,
"Error %d was returned in checking if form was available.\n",
nRet);
FPDF_CloseDocument(this->PdfDoc_);
return;
}
this->bIsLinearized_ = true;
}
}
else
{
this->PdfDoc_ = FPDF_LoadCustomDocument(File_access_.get(), nullptr);
}
if (!this->PdfDoc_)
{
unsigned long err = FPDF_GetLastError();
return;
}
(void)FPDF_GetDocPermissions(this->PdfDoc_);
PageCount = FPDF_GetPageCount(this->PdfDoc_);
}
public:
PDFManager();
~PDFManager();
void Init(char *dat, int length);
void Close();
char* GetPdfPage(int page, float& width, float& height, int& size, bool OutBmp = false);//返回長度
void ClosePdfPage(int page);
int PageCount = 0;
int PageCurrent = 0;
int PageBad = 0;
private:
FPDF_DOCUMENT PdfDoc_ = nullptr;//文件
//FPDF_FORMHANDLE Form_ = nullptr;
bool bIsLinearized_ = false; //是否線性化
FPDF_FORMFILLINFO_PDFiumTest form_callbacks_;
IPDF_JSPLATFORM platform_callbacks_;
FX_DOWNLOADHINTS Hints_;//
FX_FILEAVAIL File_avail_;
std::unique_ptr<FPDF_FILEACCESS> File_access_;
FPDF_AVAIL Pdf_avail_;
std::unique_ptr<TestLoader> Loader_;
char* File_contents_ = nullptr;
int File_length_ = 0;
std::map<int, char*> Pages_; //儲存頁面資料
};
PDFManager::PDFManager()
{
}
PDFManager::~PDFManager()
{
for (auto &buffer : Pages_)
{
delete[]buffer.second;
}
Pages_.clear();
this->Close();
}
void PDFManager::Init(char *dat, int length)
{
File_contents_ = dat;
File_length_ = length;
Options options;
options.output_format = OutputFormat::OUTPUT_BMP;
if (!File_contents_)
return;
RenderPdf(File_contents_, File_length_, options);
}
char* PDFManager::GetPdfPage(int page, float& width, float& height, int& size, bool OutBmp)
{
if (this->bIsLinearized_)
{
this->Close();
return 0;
}
if (page < 0)
return 0;
Options options;
options.currentpage = page;
options.width = width;
options.height = height;
if (!OutBmp)
options.output_format = OUTPUT_STR;
PageCurrent = page;
PageCurrent++;
return RenderPage(this->PdfDoc_, form_callbacks_, width, height, options, size);
}
void PDFManager::ClosePdfPage(int page)
{
std::map<int, char*>::iterator itor = Pages_.find(page);
if (itor != Pages_.end())
{
delete[]itor->second;
Pages_.erase(page);
}
}
void PDFManager::Close()
{
if (!this->PdfDoc_)
return;
FPDF_CloseDocument(this->PdfDoc_);
}
//介面函式
std::map<std::string, PDFManager*> g_pdfmanagersmap;
bool __stdcall PDFMANAGER_Loadpdf(const char* filename, char* dat, int length)
{
if (!filename)
{
return false;
}
if (g_pdfmanagersmap.size() == 0)
{
FPDF_LIBRARY_CONFIG config;
config.version = 2;
config.m_pUserFontPaths = nullptr;
config.m_pIsolate = nullptr;
config.m_v8EmbedderSlot = 0;
FPDF_InitLibraryWithConfig(&config);
}
std::string file = filename;
std::map<std::string, PDFManager*>::iterator itor = g_pdfmanagersmap.find(file);
if (itor != g_pdfmanagersmap.end())
{
itor->second->Init(dat, length);
}
else
{
PDFManager* pdfmanager = new PDFManager();
g_pdfmanagersmap.insert(std::make_pair(file, pdfmanager));
pdfmanager->Init(dat, length);
}
return true;
}
bool __stdcall PDFMANAGER_Closepdf(const char* filename)
{
if (!filename)
{
return false;
}
std::string file = filename;
std::map<std::string, PDFManager*>::iterator itor = g_pdfmanagersmap.find(file);
if (itor != g_pdfmanagersmap.end())
{
delete itor->second;
g_pdfmanagersmap.erase(file);
if (g_pdfmanagersmap.size() == 0)
{
FPDF_DestroyLibrary();
}
}
return true;
}
char* __stdcall PDFMANAGER_LoadPage(const char* filename, int page, float& width, float& height, int& size, bool OutBmp)
{
if (!filename)
{
return nullptr;
}
std::string file = filename;
std::map<std::string, PDFManager*>::iterator itor = g_pdfmanagersmap.find(file);
if (itor != g_pdfmanagersmap.end())
{
return itor->second->GetPdfPage(page, width, height, size, OutBmp);
}
return nullptr;
}
void __stdcall PDFMANAGER_ClosePage(const char* filename, int page)
{
if (!filename)
{
return;
}
std::string file = filename;
std::map<std::string, PDFManager*>::iterator itor = g_pdfmanagersmap.find(file);
if (itor != g_pdfmanagersmap.end())
{
itor->second->ClosePdfPage(page);
}
}
int __stdcall PDFMANAGER_GetPageCount(const char* filename)
{
if (!filename)
{
return 0;
}
std::string file = filename;
std::map<std::string, PDFManager*>::iterator itor = g_pdfmanagersmap.find(file);
if (itor != g_pdfmanagersmap.end())
{
return itor->second->PageCount;
}
return 0;
}
int __stdcall PDFMANAGER_GetCurrentPage(const char* filename)
{
if (!filename)
{
return 0;
}
std::string file = filename;
std::map<std::string, PDFManager*>::iterator itor = g_pdfmanagersmap.find(file);
if (itor != g_pdfmanagersmap.end())
{
return itor->second->PageCurrent;
}
return 0;
}
註釋說的比較清楚,就不解釋了。
3、新增模組檔案:
我取名為PdfManager.def,在裡面新增如下程式碼:
LIBRARY "Pdf"
EXPORTS
PDFMANAGER_Loadpdf @ 1
PDFMANAGER_Closepdf @ 2
PDFMANAGER_LoadPage @ 3
PDFMANAGER_ClosePage @ 4
PDFMANAGER_GetPageCount @ 5
PDFMANAGER_GetCurrentPage @ 6
即指定要編譯成dll的介面函式。
4、編譯,最後整理成pdf庫:
直接編譯release版本就可以了,通用。
三、使用封裝好的pdf動態庫:
1、在vs中使用:
1.1 先新建測試專案
1.2 新增pdf庫
1.2 新增程式碼:
main.cpp:
#include <iostream>
#include <fstream>
#include "PdfManager.h"
#include <memory>
#include <windows.h>
char* GetFileContents(const char* filename, size_t *size)
{
std::fstream instream;
instream.open(filename, std::ios::_Nocreate | std::ios::binary);
if (!instream.is_open())
{
std::printf("open file Failed!\n");
std::printf("%s\n", filename);
instream.close();
return nullptr;
}
instream.seekg(0, std::ios::end);
*size = instream.tellg();
instream.seekg(0, std::ios::beg);
char *buffer = new char[*size];
instream.read(buffer, *size);
instream.close();
return buffer;
}
int main()
{
char* name = "test.pdf";
size_t length;
std::unique_ptr<char> filecontents(GetFileContents(name, &length));
PDFMANAGER_Loadpdf(name, filecontents.get(), length);
int counts = PDFMANAGER_GetPageCount(name);
for (int i = 0; i < counts; ++i)
{
if (GetAsyncKeyState(VK_F2) & 0x8000)
break;
float width, height = 0;
int length = 0;
PDFMANAGER_LoadPage(name, i, width, height, length, true);
PDFMANAGER_ClosePage(name, i);
}
PDFMANAGER_Closepdf(name);
system("pause");
return 0;
}
結果如圖(數字.bmp是渲染出來的每一頁,我只渲染完三頁就關了):
2、在qt中使用:
2.1新建qt專案
2.2 匯入pdf動態庫
2.3關鍵程式碼(ui邏輯程式碼就不貼了,其實就是主要講怎麼用,怎麼渲染):
PDFForm::PDFForm(const char *filename, QByteArray &bytearray, QWidget *parent) :
QWidget(parent),
ui(new Ui::PDFForm)
{
ui->setupUi(this);
FileLength_ = bytearray.length();
File_ = new char[FileLength_];
std::memcpy(File_, bytearray.toStdString().c_str(), FileLength_);
FileName_ = filename;
Picture_ = new PictureBox();
Picture_->setMode(PictureBox::PB_MODE::FIX_SIZE_CENTRED );
this->ui->verticalLayout_2->addWidget(Picture_);
}
void PDFForm::InitFile()
{
if(HaveLoadPdf_)
return;
int length = (int)FileLength_;
PDFMANAGER_Loadpdf(FileName_.c_str(), File_, length);
HaveLoadPdf_ = true;
PageCount_ = PDFMANAGER_GetPageCount(FileName_.c_str());
this->LoadPage(0);
}
void PDFForm::LoadPage(int page)
{
if(!HaveLoadPdf_)
return;
int length = 0;
QRect rect = this->ui->verticalLayout_2->geometry();
float width = rect.width();
float height = rect.height();
char* Buffer = PDFMANAGER_LoadPage(FileName_.c_str(),page, width, height, length, false);
QImage image((uchar*)Buffer, width, height, QImage::Format_RGBA8888);
this->Picture_->setImage(image);
PDFMANAGER_ClosePage(FileName_.c_str(),page);//釋放頁面記憶體
UpdateLabelPage();
}
效果如下圖:
到這裡就完成了需要在qt中顯示或開啟pdf的需求,還做了適配,可以直接拉伸縮小,而且最主要的是,因為其本質是點陣圖,放大縮小時重新loadpage可以實現解析度也不斷放大縮小。
四、結語:
1、本系列到此結束,其實還有些東西,比如在qt裡做顯示適配,例如上面的Picture_物件就是自定義的一個image類,在介面上顯示時方便居中,要寫的話還可以寫第五篇,但是我暫時沒空,就打住了,以後會不會補需要再看看。
2、本次研究說實話讓我提升很多,很多是思維和經驗上的改變,獨立能力稍微有點加強,希望能早日成為大牛。
17.05.19更新:
程式碼地址:
傳送門
17.07.27更新:
大家不用留郵箱了,我不是經常上這個帳號,下載連線也貼了,也不花積分,直接下載就好了(ps:我自己下了,也叫別人下了,檔案沒問題,下載下來有問題重新試試,csdn是經常抽風,網路不是很穩定)
17.08.09更新:
鑑於很多人問我要在QT中開啟的demo,現在補上(如果覺得不錯,不妨點個頂或者關注,你的鼓勵是對我最大的支援):
傳送門
另外 需要1積分,不知道為啥,現在csdn資源最少1積分,包括我以前的0分資源全部自動調整為1分,特此說明。