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4.3.2 C#

3. Add the following namespaces:

Example:

using Pdftools.Pdf;

using Pdftools.PdfRenderer;

using Pdftools.Pdf2Img;

4. The .NET interface can now be used as shown below:

Example:

using (Converter conv = new Converter())

{

conv.Open(...);

...

}

4.3.3 Deployment

This is a guideline on how to distribute a .NET project that uses the 3-Heights™ PDF to Image Converter API.

Detailed description

1. The project must be compiled using Microsoft Visual Studio. Hereby it is cruciual that the solution platform (x86

or x64) matches the platform of the native DLL

Pdf2ImgOCX.dll

2. The executable is created in the directory

bin\Release

3. For deployment, the executable and all .NET assemblies must be copied into the same folder on the target

computer. The .NET assemblies of the 3-Heights™ PDF to Image Converter API have the ﬁle name

*NET.dll

4. At runtime, the native DLL

Pdf2ImgOCX.dll

must be found on the target computer by the DLL search se

quence. To ensure this, the DLL must either be copied to the folder containing the executable or to a directory

on the environment variable

Path

(e.g.

%SystemRoot%\system32

5. If required by the application, optional DLLs such as

pdcjk.dll

must be copied to the same folder. SeeDe

ployment

for a list and description of optional DLLs.

Simpliﬁed description

1. Compile the project using Microsoft Visual Studio.

2. Deploy your executable and all ﬁles in the directory

bin

of the 3-Heights™ PDF to Image Converter API’s instal

lation directory to the same directory on the target computer.

4.3.4 Troubleshooting: TypeInitializationException

The most common issue when using the .NET interface is that the correct native DLL

Pdf2ImgOCX.dll

is not

found at execution time. This normally manifests when the constructor is called for the ﬁrst time and an exception

of type

System.TypeInitializationException

is thrown.

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This exception can have two possible causes, distinguishable by the inner exception (property

InnerException

System.DllNotFoundException:

Unable to load DLL

"Pdf2ImgOCX.dll"

: The speciﬁed module could

not be found.

System.BadImageFormatException:

An attempt was made to load a program with an incorrect format.

The following sections describe in more detail, how to resolve the respective issue.

Troubleshooting: DllNotFoundException

This means, that the native DLL

Pdf2ImgOCX.dll

could not be found at execution time.

Resolve this by either:

adding

Pdf2ImgOCX.dll

as an existing item to your project and set its property "Copy to output directory"

to "Copy if newer", or

adding the directory where

Pdf2ImgOCX.dll

resides to the environment variable

Path

, or

copying

Pdf2ImgOCX.dll

to the output directory of your project.

Troubleshooting: BadImageFormatException

The exception means, that the native DLL

Pdf2ImgOCX.dll

has the wrong "bitness" (i.e. platform 32 vs 64 bit).

There are two versions of

Pdf2ImgOCX.dll

available: one is 32-bit (name of product kit download contains

WIN32

) and the other 64-bit (name of download contains

X64

). It is crucial, that the platform of the native DLL

matches the platform of the application’s process.

The platform of the application’s process is deﬁned by the project’s platform conﬁguration for which there are 3

possibilities:

AnyCPU

This means, that the application will run as a 32-bit process on 32-bit Windows and as 64-bit process

on 64-bit Windows. When using AnyCPU one has to use a diﬀerent native DLL, depending on the platform of

Windows. This can be ensured either when installing the application (by installing the matching native DLL)

or at application start-up (by determining the application’s platform and ensuring the matching native DLL is

loaded).

x86 This means, that the application will always run as 32-bit process, regardless of the platform of the Windows

installation. The 32-bit DLL runs on all systems, which makes this the simplest conﬁguration. Hence, if an ap

plication needs to be portable and does not require any speciﬁc 64-bit features, it is recommended to use this

setting.

x64 This means, that the application will always run as 64-bit process. As a consequence the application will not

run on a 32-bit Windows system.

5User’s Guide

5.1 Supported Codecs

The following table lists which capabilities of the diﬀerent codecs are supported by the 3-Heights™ PDF to Image

Converter API.

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Codec Capabilities

Codec

Bits per Pixel

Gray

Indexed

Quality

Compression

TIFF

1,2,3,4,8,24

Yes

Raw, Flate, LZW, JPEG, Group3, Group3_2D, Group4

JPEG

8, 24

Yes

JPEG (lossy only)

BMP

1, 2, 4, 8, 24

Yes

Raw

GIF

2-8

Yes

LZW

PNG

1-8, 24

Yes

Flate

JBIG2

Yes

JBIG2 (lossless only)

JPEG2000

8, 24

Yes

JPEG2000 (lossless: Q = 100)

PBM

1-8, 24

Yes

Raw

EPS

1, 2, 4, 8, 24

Yes

Raw

Codec The Compression/Decompression Type.

Bits Per Pixel The supported values for bits per pixel. 1 = bi-tonal, 8 = 256 colors/grey scales, 24 = True Color

Gray This format supports grey scale.

Indexed This format supports indexed colors.

Quality This format supports the setting of a quality parameter.

Compression Supported compression types.

5.1.1 File and Compression Type

Most image types have a predeﬁned compression algorithm. For TIFF, the type of compression can be selected

manually.

JPEG2000 (PDF 1.5) and JBIG2 (PDF 1.4) formats allow the compression rate to be adjusted via a quality parameter.

These two formats are of newer date and will not work with older PDF software.

Here are some suggestions of what image type could be selected for which purpose.

Lossless

For palette creation: The number of palette entries is equal to 2BitsPerPixel where BitsPerPixel is smaller or equal to 8. This means it is possible

to create a 3 bits per pixel TIFF or BMP, but the palette size is equal as for 4 bits. However the 3 bits per pixel image will compress better than the

4 bits per pixel image.

To create lossless JPEG2000 images, set the quality parameter to 100. For values <100, a lossy compression algorithm is applied.

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Black/White JBIG2 (Q = 100) or TIFF with G4 compression

Gray scale PNG, JPEG2000 (Q = 100)

Color PNG, JPEG2000 (Q = 100)

Lossy

Black/White JBIG2

Gray scale JPEG, JPEG2000

Color JPEG, JPEG2000

For the Internet

Black/White PNG

Color (Photos) JPEG, PNG

Color (Artiﬁcial) GIF, PNG

As a general note: Compression algorithms that are lossy require more CPU as lossless algorithms. The ﬁle size is

usually smaller but the time to create (compress) or read (decompress) the ﬁle is higher.

Images formats that are supported by most Internet browsers are JPEG, GIF and PNG.

5.2 How to Create Multi and Single-Page Images

5.2.1 Multi-Page Images

The TIFF format is an image format which supports multi-page images.

To create multi-page TIFF images, just keep rendering pages, and open/close PDF documents without closing the

TIFF image.

5.2.2 Single-Page Images

To create single-page TIFF images, render one page, close the image and create a new image ﬁle.

5.3 How to Set Pixels Equal Points

How to create images with pixel (in image) equal to points (in PDF)?

The default value of the resolution in the created image is 150 dpi. The PDF format uses a resolution of 72 dpi. In

order to create an image with as many pixels per dimension as the PDF had in points, use an image resolution of 72

dpi as well. Please note that generally this yields in a grainy image when viewed at 100% zoom, since the monitor

uses a resolution of 96 dpi.

5.4 How to Reduce the File Size

There are diﬀerent ways to reduce the ﬁle size of an image. One needs to be aware that from a certain point on, a

smaller ﬁle size results in a poorer visual quality.

The main factors on which the ﬁle size of an image depends are:

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Dimensions in pixel (width and height)

Bits per pixel

Compression Type

The content of the image (inﬂuenced by dithering)

5.4.1 Dimensions

Reducing the dimensions and therefore the amount of the total pixels reduces also the ﬁle size. Obviously a

1024x768 pixel image has a larger ﬁle size than an equivalent 600x480 image.

To set the dimension in pixels, use a command like this:

SetBitmapDimensions(600, 480)

To set the dimension in points, use a command like this:

SetPageSize(600, 480)

If the dimensions are set in points, the dimensions in pixel are calculated depending on the resolution.

5.4.2 Resolution

The resolution in dots per inch (DPI) lets you specify how detailed the image is. The default value is 150 dpi, which

generates an image that looks sharp when not zoomed into. A larger value generates a more detailed image, but

also will increases the ﬁle size, because it requires more pixels. On the other hand, a lower resolution generates a

ﬁle with a smaller ﬁle size, but the image is also of lower visual quality.

Setting the resolution value to 75 DPI instead of 150 DPI reduces the ﬁle size to about one quarter:

dpi = 75

5.4.3 Bits per Pixel

Using 1-bit (black/white) or 8-bit grey scale instead of 24-bit true color will reduce the ﬁle size. Keep in mind that

not all formats support all color depths.

BitsPerPixel = 8-b 8

5.4.4 Format/Compression Type

The 3-Heights™ PDF to Image Converter API supports various image formats. For most formats the compression is

given. For example a PNG image is always Flate-compressed, a JPEG image is always JPEG-compressed. However

for TIFF, the compression type is selectable.

Images formats that are supported by most Internet browsers are JPEG, GIF and PNG.

There are two fundamentally diﬀerent types of compression: Lossless and lossy.

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Lossless compressionThe transformation from the original to the compressed state of the image does not change

the content. Thus the transformation is reversible and the original image can be regained from the compression

state.

Lossless compression is normally used for artiﬁcial images or scanned text. It is applied to the following types of

images: GIF, PNG, BMP, JPEG2000 if quality is set to 100, JBIG2 if quality is set to 100 and TIFF compressed with G3,

G4, LZW or Flate.

Lossy compression n The compression algorithm alters the content of the image in a way that it compresses better.

Thus a lossy compressed image cannot be reverted back to its original state. It also means multiple applications of

lossy compression to the same image alter the image every time and thereby reduce the quality every time. How

much the image may be altered to improve the compression rate is controlled by a quality index ranging from 1 to

100 and normally defaulted at 75.

Lossy algorithms usually provide a better compression rate, at the cost of visual quality. Lossy compression is nor

mally used for photographs.

It is applied to the following types of images: JPEG, JPEG2000 if quality is less than 100 and JBIG2 if quality is less

than 100.

There are various compression types supported for the TIFF image format. These are:

CCITT Group 3, Group 3-2D

CCITT Group 3 is the predecessor to CCITT Group 4, it is a simpler algorithm that

normally results in a lower compression ratio.

CCITT Group 4 CCITT Group 4 is the standard compression for bi-level TIFF images (i.e. facsimile).

LZW

LZW (Lempel-Ziv-Welch) compression is a lossless compression algorithm for images.

Please consult the copyright laws of your country prior to using this compression algorithm.

JPEG

TIFF allows images to be compressed with JPEG, which is a lossy compression algorithm. JPEG provides a

high compression ratio for 8 and 24 bit images. It is best suited for TIFFs containing photographs and little or

no text.

ZIP (Flate) ZIP is a lossless compression algorithm. It is useful for the compression of large images with no loss in

quality.

Flate compression (also used by the ZIP format) and JPEG compression can be used for color or grey scale images.

CCITT Group 3, 3-2D and 4 as well as Flate can be used for black and white images.

Example: Apply Flate compression to a TIFF Image

Compression = eComprFlate

5.4.5 Image Content, Dithering

The content of the image itself has a direct impact on how well it compresses. It seems quite obvious that a plain

white image compresses much better than a page ﬁlling photograph.

Dithering is an algorithm that arranges the pixels of an image in a way that it creates a visual eﬀect of colors that do

not exist in the available colors of the image, such as diﬀerent grays in a 1-bit black and white image. This complex

arrangement of pixels however does not compress well and increase the ﬁle size. Disabling dithering therefore

reduces the ﬁle size. In the PDF to Image Converter, dithering is also implemented for color images.

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Example: disable dithering (e.g. for scanned text)

Dithering = eDitherNone

For more information, see chapterDithering

5.5 How to Use the In-Memory Methods

An image created by the 3-Heights™ PDF to Image Converter API can consist of multiple pages. For example if

the image format supports multiple pages, such as the TIFF envelope and

RenderPage

is called multiple times.

CreateImageInMemory

needs to be called for every image created.

GetImage

returns a byte array holding

the image. Its length can be retrieved applying the appropriate length-operator of the programming language you

are using.

5.5.1 Creating a Document in Memory

Here is a Visual Basic 6 sample that opens a document from ﬁle, creates the image in-memory and saves it to the

variant pdfbytes.

Private Sub ConvertInMemory_Click()

Dim conv As New PDF2IMGOCXLib.Pdf2Img

Dim pdfbytes As Variant

Dim length As Long

conv.Open "C:\input.pdf"

conv.CreateImageInMemory ".tif"

conv.RenderPage 1

conv.RenderPage 2

pdfbytes = conv.GetImage

length = LenB(pdf)

conv.CloseImage

conv.Close

End Sub

5.5.2 Reading a Document from Memory

The Visual Basic 6 code below opens a document from memory.

In part (1) the document is written into a byte array, this part is just a sample; it could as well be replaced by a process

reading the byte array from a data base.

In part (2) the document is actually opened from memory.

Private Sub OpenFromMemory_Click()

' (1) Write PDF document to memory

Dim conv As New PDF2IMGOCXLib.Pdf2Img

Dim bChar() As Byte

Dim lFileLenght As Long

Open "C:\input.pdf" For Binary As #1

lFileLenght = LOF(1)

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ReDim bChar(lFileLenght - 1)

Get #1, , bChar

Close #1

' (2) open document from memory

If Not conv.OpenMem(bChar, "") Then

MsgBox "couldn't open document"

End If

End Sub

5.6 Color Proﬁles

A PDF document may contain graphical objects using various diﬀerent color spaces and the output ﬁle of 3-

Heights™ PDF to Image Converter API may yet use another color space. Therefore often colors have to be converted

between diﬀerent color spaces.

For calibrated color spaces (such color spaces with an associated ICC color proﬁle) the color conversion is well de

ﬁned. For the conversion of uncalibrated device color spaces (DeviceGray, DeviceRGB, DeviceCMYK) however, the

3-Heights™ PDF to Image Converter API requires apropriate color proﬁles. Therefore it is important, that the proﬁles

are available and that they describe the colors of the device your input documents are intended for.

Note: When setting an alternative color management system such as Neuge

bauer, no color proﬁles are required.

If no color proﬁles are available, default proﬁles for both RGB and CMYK are generated on the ﬂy by the 3-Heights™

PDF to Image Converter API.

5.6.1 Default Color Proﬁles

If no particular color proﬁles are set default proﬁles are used. For device RGB colors a color proﬁle named

"sRGB Color Space Profile.icm"

and for device CMYK a proﬁle named

"USWebCoatedSWOP.icc"

are

searched for in the following directories:

Windows

%SystemRoot%\spool\drivers\color

2. directory

Icc

, which must be a direct sub-directory of where the

Pdf2ImgOCX.dll

resides.

5.6.2 Set other Color Proﬁles

Other color proﬁles may be set using the methods

SetsRGBProfile

and

SetCMYKProfile

5.6.3 Get Other Color Proﬁles

Most systems have pre-installed color proﬁles available, for example on Windows at

%SystemRoot%\sys-

tem32\spool\drivers\color\

. Color proﬁles can also be downloaded from the links provided in the direc

tory

bin\Icc\

or from the following websites:

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http://www.pdf-tools.com/public/downloads/resources/colorprofiles.zip

http://www.color.org/srgbprofiles.html

https://www.adobe.com/support/downloads/iccprofiles/iccprofiles_win.html

5.7 Fonts

PDF documents may contain both embedded and non-embedded fonts. When rendering non-embedded fonts

the best result can be achieved, if the font is available on the system. Therefore it is important to make sure the font

directories contain all fonts required.

For more information on how to cope with font issues, please refer to sectionFont and Text Issues

5.7.1 Font Directories

The location of the font directories depends on the operating system. All fonts of all font directories are added. Font

directories are traversed recursively.

Windows

%SystemRoot%\Fonts

2. directory

Fonts

, which must be a direct sub-directory of where the

Pdf2ImgOCX.dll

resides.

5.7.2 Font Conﬁguration File fonts.ini

The font conﬁguration ﬁle is optional. It can be used to control the mapping of fonts used in the PDF to fonts

pre-installed on the system.

The ﬁle

fonts.ini

must reside at the following location :

Windows: In a directory named

Fonts

, which must be a direct sub-directory of where the

Pdf2ImgOCX.dll

resides.

It consists of two sections:

[fonts]

and

[replace]

. Both sections are used to map fonts in the PDF to fonts in

the installed font collection on the operating system. This comes into play when the font in the PDF document does

not have an embedded font program, or the embedded font is not usable.

The mapping only works if the font types of the speciﬁed fonts are matching; e.g. if the font in the PDF is a symbolic

font, such as“Symbol” or“ZapfDingbats”, the mapped font must be symbolic too.

The section

[fonts]

is only considered if the font-matcher does not ﬁnd an appropriate font amongst the existing

installed fonts. It is suggested to only use this section.

The section

[replace]

is stronger and applied before the font-matcher. This means a font will be replaced as

deﬁned, even if the correctly installed font is available on the system.

Syntax: The syntax of the mapping ﬁle is as follows

[fonts]

PDF_font_1=installed_font_1{,font_style}

PDF_font_2=installed_font_2{,font_style}

[replace]

PDF_font_n=installed_font_n{,font_style}

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PDF_font_* is the name of the font in the PDF. This name can be found in one of the following ways:

Use any tool that can list fonts. Such as 3-Heights™ PDF Extract or 3-Heights™ PDF Optimizer. Ignore possible

preﬁxes of font subsets. A subset preﬁx consists of 6 characters followed by the plus sign. For example

“KHFOKE+MonotypeCorsiva”, in this case only use“MonotypeCorsiva” as font name in the mapping ﬁle.

Open the document with Adobe Acrobat, use the“MarkUp Text Tool”, mark the text of which you would like

to know the font name, right-click it, select “Properties...”

installed_font_* is the font family name of the installed font. To retrieve this name, ﬁnd the font in the Windows’

font directory and open it by double-clicking. The ﬁrst line in the property window displays the font family name

(this may vary depending on the operating system). The font family name does not include font styles; so an

example of a font family name is“Arial”, but not“Arial Italic”.

font_style is an optional style, that is added coma-separated after the font family name. The style is always one

word. Examples of font styles are “Italic”, “Bold”,“BoldItalic”. Omit the font style, if it is “Regular”or“Normal”.

Remove blanks from all font names, i.e. both the

PDF\_font

and the

installed\_font

Example:

[fonts]

Ryumin-Light=MSMincho

GothicBBB-Medium=MSGothic

[replace]

ArialIta=Arial,BoldItalic

5.8 How to Change the Colors - Receive a Darker Black

CMYK colors that are used in the PDF must ﬁrst be converted to RGB. There are basically two ways how to achieve

this:

1. A CMYK color proﬁle is applied. The suggested default color proﬁle is the“U.S. Web Coated (SWOP) v2”. Using a

diﬀerent color proﬁle yields in an image output with diﬀerent colors. See

SetCMYKProfile

SetsRGBPro-

file

RGB and CMKY color proﬁles can be found on the Windows systems at following location:

%System-

Root%\system32\spool\drivers\color

2. The Neugebauer algorithm is applied for the color conversion using the function

SetCMSEngine

and the path

to the text ﬁle holding custom coeﬃcients as argument.

Sample Visual Basic 6 code snippet:

Dim conv As New PDF2IMGOCXLib.Pdf2Img

' Set the color management engine

conv.SetCMSEngine App.Path & "\CmykToRgb.txt"

The default Neugebauer coeﬃcients convert CMYK black (0, 0, 0, 1) to an RGB black which is not pure black. The fol

lowing coeﬃcients will create a darker black. The changes are applied on line 5 (originally ~0.2, see SetCMSEngine).

To receive a darker black, the values for k need to be lowered even more.

0.996078, 0.996078, 0.996078 ; White

0.000000, 0.686275, 0.937255 ; C

0.925490, 0.149020, 0.560784 ; M

1.000000, 0.949020, 0.066667 ; Y

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