Processing PDF and JPG files in VB6

A recent project needs pdf The file page is output as jpg Picture file , And then for these outputs jpg Page clipping .

because VB6 It's old , Many mainstream plug-ins do not vb6 Usable api Or sample code , I've been looking for it on the Internet for a long time , To sum up VB6 Feasible plan ：

One 、 Handle pdf file

1.Apache PDFBox

PDFBox It's a use Java Open source PDF Document processing library
Download here ：
http://pdfbox.apache.org/

Because it's using Java Compiling , So you need to install... Before use jre
The program supports command line , stay VB The specific calling method in is shell（） Command invocation , for example ：

shell ("java -jar pdfbox-app-2.0.4.jar PDFToImage -imageType jpg C:\1.pdf")

The above command will be a pdf All pages of the file are output as jpg picture , There are many other commands that can be used , Specific reference ：
http://pdfbox.apache.org/2.0/commandline.html

PDFBox One big disadvantage is that the processing speed is slow

2.Debenu Quick PDF Library

Debenu At present, it has been used by domestic Foxit Fuxi acquired , It's a commercial software , You need to pay for it , But you can find the registration code online .
Required after download ActiveX Of quickpdf.dll and quickpdf.tlb Two documents , You can use the system's own Regsvr32 register quickpdf.dll, Or not , If there is an error running on other computers, you need to register .

menu bar - engineering - quote , Select browse , Choose quickpdf.tlb Later, this library was referenced in the project ：

Next , Can press F2 Check the objects that can be called in this library , The complete development documentation is here ：
http://www.debenu.com/products/development/debenu-pdf-library/help/developer-guide/

The next step is to enter the actual development process , Because it's commercial software , First, you need to enter the registration information ：

Dim pb As New DebenuPDFLibraryAX1016.PDFLibrary
Dim RegStatus As Integer
RegStatus = pb.UnlockKey("j87ig3k84fb9eq9dy34z7u66y")
Print RegStatus

If it returns RegStatus by 1, It indicates that the registration is successful

take PDF The page is converted into a picture file ：

QP.LoadFromFile("sample.pdf", "")          ' The first step is to load the file into memory 
iNumPages = QP.PageCount()          ' obtain pdf Number of pages of the file 
QP.RenderDocumentToFile(100, 1, iNumPages, 0, "image.bmp")  ' transformation 

For other commands, please refer to the development documentation

Two 、 Handle jpg image file

There are two solutions offered online ： Use GDI+; call Intel JPEG lib. Here is another open source solution FreeImage, Support jpg、png、bmp And other image processing , Download here dll And development documentation ：
http://freeimage.sourceforge.net/download.html

The required files are in the compressed package FreeImage.dll and modFreeImage.bas, Put the two files in the program directory .

Build a new project , take modFreeImage.bas Add as a module , So you can call dll 了 .

Resample the image ：

Dim dib As Long
Dim dib2 As Long
dib = FreeImage_LoadU(FIF_JPEG, "jpgfile.jpg",0)    ' Load pictures into memory 
dib2 = FreeImage_Rescale(dib, 1280, 800, FILTER_BOX)    ' Resampling 
Call FreeImage_SaveU(FIF_JPEG, dib2, "tgfile.jpg",0)    ' Save the file 
FreeImage_Unload(dib)                   ' Free memory