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2. Basics of Image Processing

## 2.13 File Formats

Picture file formats are an unpleasant topic in image processing. There exists an enormous amount of formats and each format has its weaknesses. No format (with the exception of the PhotoLine format PLD) is able to store all things that can be done with PhotoLine.

There is another problem. Standard file formats are by far not as "standard" as their name may sound. And many formats are simply too complex, so there is no application that is able to load all possible variations.

Now we will show the most important file formats.

PLD

PLD is the PhotoLine defined file format. It is able to store all kind of information in a document such as pages, image layers, vector layers, text layers and groups. Aside from this, special information like printer settings, animation data and so on is stored, too. It is recommended to save pictures created with PhotoLine as long as possible as PLD file. You should only save in a different file format if you plan to use the picture with another application because saving in another format nearly always goes hand in hand with a loss of information.

PDF

PDF has become the standard format for exchanging multipage documents. One of the advantages of PDF is its ability to contain text, images and vector graphics. PDF files are usually viewed and printed with Adobe Reader™ from Adobe®.

PhotoLine can read and write PDF files, but there are some restrictions on reading: due to the many features of PDF, PDF files are not always read correctly.

PDF files are well suited to exchange documents containing text and vector graphics.

TIFF

TIFF is a very common file format with the advantage to be used on different hardware platforms. TIFF offers some advantages like storing of bitmaps, gray images, RGB images and CMYK images. It is able to store transparency, too. It is possible to save several image layers to a TIFF file, but only few applications are supporting this.

Bitmaps can be compressed at a high rate by using TIFF Fax4.

You shouldn’t use the compression TIF-JPEG because many applications can’t read this compression.

If you have problems reading TIFF files with other applications, you should set the compression in Options/File/TIF to TIF-uncompressed.

We recommend the TIFF file format for the data exchange between different applications.

GIF

GIF has got undeserved fame through its use in the internet area. GIF is able to store images with up to 256 colors. One of these colors can be defined to be transparent.

GIF stores image data with LZW compression. This compression method achieves only mediocre results.

It is possible to save several images to one file. Therefore, GIF can be used for small animations.

GIF should only- if ever - be used for web graphics.

BMP

BMP is the standard image file format for Windows. But it can store neither layers nor transparency. Compression is low, with run length encoding (RLE) or not existent.

BMP is well suited for data exchange with Windows applications.

JPEG

JPEG is a commonly used format. It is able to store gray, RGB and CMYK images. Unfortunately, transparency and layers are not supported.

The largest advantage of JPEG is it high compression of image data.

But this compression is lossy, therefore, you should avoid to process JPEG saved images any further.

PhotoLine is able to read ICC color profiles, that are embedded in an JPEG, and to export them again. Additionally, it can read and write clipping paths (see chapter 5.5.5).

Because of the high compression rates, JPEG should be used for web graphics and for archiving images.

JPEG 2000

JPEG 2000 was designed as successor of JPEG, but until now it hasn‘t been able to succeed. JPEG 2000 main goal was to create smaller files while getting the same quality compared to JPEG. But in reality, this goal hasn‘t been fully met. Depending on the theme, it‘s possible to get smaller files, but most of the time the resulting files are not significantly smaller. If you additionally take the minor support compared to JPEG into consideration, JPEG 2000 can not be recommended.

JPEG XR

JPEG XR was also developed as a successor to JPEG. However, it could not become generally accepted until today. Compared to JPEG, this should also allow smaller files with the same quality.

JPEG XL

JPEG XL is another format developed as a successor to JPEG. It can store 8-, 16- and 32-bit images. Whether it will achieve any significance remains to be seen.

PNG

PNG is a format, which was invented for replacing GIF on the internet. It offers some advantages like a very good compression and the ability to store full transparency. It doesn’t store layers.

Raw: Digital Camera Raw Format

Many digital cameras can save a so-called Raw format. This format saves the raw data that come "directly" from the sensor of the camera. This format has some advantages and disadvantages compared to other file formats. The main advantage is, that the images are relatively small and there are no compression problems. You avoid problems with the automatic color correction of the camera, too. The disadvantage is that every camera has its own raw format. So you have to search for an application, that can read the format of your camera. If you have such a software, you will see, that you have to spend some time to get a perfect image from your raw data.

PCD/Photo CD

PCD was developed to save color photos on CD. One file contains the photo in several sizes: Base/16, Base/4, Base, Base*4, Base*16 and sometimes Base*64.

PCX

PCX is an old file format and no longer widely used. You should use PCX only in special cases.

WMF

WMF is a Windows specific file format. It is able to store images, vector objects and text. Because of the complexity of WMF reading and writing is error-prone. Therefore, you should avoid this format.

EMF

EMF is the successor of WMF. It offers the advantage of being able to use a larger coordinate system and storing curves.

PICT

PICT was the macOS counterpart to WMF. It is able to store images, vector objects and text. With macOS, PICT was replaced by PDF and TIFF, so that PICT isn't important anymore.

SVG (Scalable Vector Graphics)

The capabilities of SVG are similar to those of PDF. An SVG file can contain text, vector graphics and raster images. It is mainly used for web pages.

PhotoLine can read and write SVG files.

OpenEXR

OpenEXR is an HDR (High Dynamic Range) file format and intended for saving images with 32 bits per color channel. OpenEXR files can contain several layers.

PhotoLine can read and write Open EXR files.

PS and EPS

PS and EPS are file formats, that were commonly used in the printing industries. For many years now, they have been replaced by PDF.

On Windows PhotoLine doesn't support EPS and PS directly, on macOS the OS is used for importing them.

In order to enhance the import, you can use the open source software Ghostscript.

On Windows, Ghostscript has a DLL (Dynamic Link Library). If you place this DLL in the Hlp-directory of PhotoLine, PhotoLine will use it for importing. The 32-bit version of the DLL must be named "gsdll32.dll" and the 64-bit version "gsdll64.dll".

On macOS, PhotoLine uses the command line version of Ghostscript.

FITS (flexible Image Transport System)

FITS is a file format used for scientific data and astronomy. PhotoLine can read FITS.

SER

SER is a simple video format used in astrophotography. PhotoLine can read SER.