\b0\fs24 ImageConverter is a NEXTSTEP program designed for converting 12 bit grayscale radiographic images into TIFF format. Radiology has standardized on a 12 bit per pixel (4096 grayscale) format for storing images. For digitized X-Rays, this insures that as much of the original detail of the film is contained in the digital image, and for computed tomography studies, the original Hounsfield values (ranging from -1000 to +3000) are preserved.\
ImageConverter will convert any ACR/NEMA 2.0 or DICOM 3.0 image into TIFF. Many of these images have proprietary headers. ImageConverter ignores the header, and the user interactively creates a new header for the image using an easy to use graphical interface.\
\b\fs36 Image Format\
\b0\fs24 Radiographic images are 12 bits per pixel, or 1.5 bytes per pixel. However, pixels must fall within byte boundaries. Therefore, 16 bits, or two bytes, are used for each pixel, and the highest 4 bits are discarded.\
Depending on the architecture of your computer (Big Endian vs. Little Endian), the two bytes of each pixel are stored either with the Most Significant Byte (MSB) first or with the Least Significant Byte (LSB) first.\
ImageConverter allows the user to determine byte ordering with two radio buttons that alternately swap or don't swap byte pairs.\
\b Headers
\b0 \
Different images have different length headers, depending on the format and vendor specific information. ImageConverter initially sets the size of the header to 0 bytes. The user has the option to specify the number of bytes to offset from the beginning of the file to the location where the image actually begins.\
\b Resolution:
\b0 \
The user must enter the width of the image in pixels. ImageConverter calculates the height of the image automatically from the width and the size of the file.\
\b Beightness and Contrast:\
\b0 From the 12 bpp image, ImageConverter creates an 8 bpp TIFF image. The user specifies the brightness and contrast values that best show the image. After graphically manipulating the Brightness and Contrast sliders, the user must press the
\i Display
\i0 button to update the image.\
\b\fs36 Saving Images:\
\b0\fs24 Images can be saved to standard TIFF format for use in other programs. The
\i Save To Tiff
\i0 menu option freezes the image to TIFF with the current contrast, brightness, and scale.\
The image on screen is an exact representation of the TIFF file that will be created. Irrespective of your conputer's screen color mode, ImageConverter always displays the image in 8 bpp grayscale. Thus, the program will run much faster when the color mode of the screen allows the image to be displayed without any dithering (ie. wien running in 8 bit grayscale or 24 bit color mode). Running NEXTSTEP in 12 bit color or 2 bit grayscale gives much slower performance, though the final image is not affected.\
\b\fs36 Future Plans:\
\b0\fs24\fi-340\li360 - Improved contrast and brightness controls to allow non-linear window levels\
- Store and load preset LookUpTables (LUT) for different types of images such as plain film, CT, and MRI.\
- Automatically interpret DICOM 3.0 headers\
- Tools for cropping, edge-enhancement, and other features\
- A text window that allows the user to inspect the header of the original image\
(.txt)