Prezentace v angličtině: DNG Reader

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DNG Reader

The programm is wrote in JAVA, the mail of the programm is transform of the DNG file into two dimensional matrix for the import to the Matlab, which is a sofistic mathematical software.

It also

It can extract the additional image inforamtion called EXIF (Exchangeable image file format). It contains information about camera setting in the moment of the exposure.

The programm enables creating histograms (of the light intensity distribution) too.

The image don't look very nice, but don't be scared. That is the reason, why it is not prooperly displayed.

Matrix

This is an example of the giant matrix. It has about 27 megabyte

Conclusion

The extracting the image data

Some futher image processing will be needed

explain raw data - image data before processing in the camera, contains data, that human eyes don't recognise, but it is important form computer processing

Goals

We don't want display data on a computer monitor, but we need data for next computing...

Motivation

Camera sensor (chip) contains/consists milions of light sensitive pixels, (that we can imagine as a small cells...) that are arranged into two dimensional matrix/array. But only three colors is captured: red, green and blue (RGB). /the pixels are sensitiv to three colors: RGB... Each pixel is generally sensitive to all three color but...

For this is on a sensor a structure called Bayer mask (filter). It looks like this [image Bayer mask] The rectangle contains one red pixel, one blue pixel and two green pixel. In the fact, we are able to contain only one third pixel of the total number of pixels... But image data are recomputing (demosaicing process), so that each pixel contains all of the three color...

demosaicing process - computes a color from the four neightboring pixel, color interpolation...

Color depth is among of the light, that each pixels are able to capture.

The structure of the camera sensor.

Pixels are distributed in the Bayer mask structure.

the demosaicing process... the

File formats

JPEG - the most common, many camera use it for storage image data

It's used in most camera. It doesn't contain the original image data.

The files are relatively small and threre are no problem display it on a computer.

Some information are loss because of compressing...

The compression is not usualy visible for human eyes, but for computer processing more information is loss.

We don't see what the camera saw...

TIFF - the data are processed too, not contains raw data

RAW

the name cames from unprocessing image data

Manyfacturer dependent format - each camera producer have specific format of RAW and that can be problem with displaying it in the future (because of noncompatibility with operating systems and so on...)

For example the Olympus has extension orf (Olympus raw format), and it can mostly read only software from Olympus... and so on...

Can't be displayed in the camera.

The versions are not compatibilite with each other...

DNG

called Digital negativ - the name after analogue digital negative, have to remember, that there are raw data, unprocessed

the name refers to raw data

maked by Adobe [adoube:], file format, "founded" in 2004

Adobe Systems - software corporation

have to unite/unify the formats as for example PDF

Unifynes various versions of RAW format. It is convertable from many RAW formats...

Structure of a DNG file

DNG specification contains over 200 pages in American english and it was without EXIF and private tags.

Derived from the TIFF file format

image file header - contains basic information

Binary file - we must perfect know its structure

With the current proprietary camera raw formats, software programs wishing to process

camera raw files must have specific information about the camera that created the file. As new

camera models are released, software manufacturers (and by extension users) must update

their software to accommodate the new camera raw formats.

Because DNG metadata is publicly documented, software readers such as the Adobe

Photoshop Camera Raw plug-in do not need camera-specific knowledge to decode and process

files created by a camera that supports DNG. That means reduced software maintenance and a

more self-contained solution for end users.

Image file directory

- can be more then one (for example full-size image, thumbnails...)

- extra IFD contains EXIF information

Tag - in specification there are id number and names of tags.

Type - in DNG there are 13 types of values, every must be handled by specific function because of various length of them.

Directory entries - in fact they are /contains pointers at specific place in a file, where values are hold/stored.

Example of the tags

Image data are devided into many strips, it is not stored in one matrix...