Load DICOM images in the same way as you load images of other formats. Use DICOM format options to set specific features for image loading.

Transfer Syntaxes

There are two ways to specify transfer syntax (compression) for DICOM image saving: SaveFormat parameter, and TransferSyntax DICOM format option. SaveFormat is an easy-to-use shortcut, while TransferSytnax option provides the full selection of transfer syntaxes for image saving.

Saving DICOM Images Using JPEG Compression

JPEG Lossy Baseline or Extended

This is the default mode for saving DICOM images with JPEG compression in ImageGear. In this mode:

• ImageGear saves grayscale images as either 8 bits per pixel, using "JPEG Baseline (Process 1)" transfer syntax, or as 9..12 bits per pixel, using "JPEG Extended (Process 2 & 4)" transfer syntax. 
• ImageGear saves RGB images as 24 bits per pixel, using "JPEG Baseline (Process 1)" transfer syntax.

If the source image colorspace is different from RGB or grayscale, or the bit depth is greater, ImageGear automatically converts image rasters to one of the supported pixel formats on saving. See PixelFormat ConversionduringImageSaving for more details.

As part of JPEG Lossy compression process, ImageGear converts RGB rasters into YCbCr colorspace (or YCC in DICOM terminology) during saving. This conversion is fully encapsulated into the ImageGear JPEG codec; the application should not convert images to YCbCr before saving them to JPEG or DICOM JPEG.

Use one of these ways to save an image as DICOM JPEG Baseline or Extended:

• Save the image as ImGearSavingFormats.DICOM_JPEG (SaveSyntax parameter is ignored)
• Save the image as ImGearSavingFormats.DICOM and set SaveSyntax to ImGearDICOMTransferSyntaxes.JPEG_LOSSY
• Save the image as ImGearSavingFormats.DICOM and set SaveSyntax to ImGearDICOMTransferSyntaxes.JPEG_EXTENDED_PR_2_4

JPEG Lossy Baseline Only

This mode provides compatibility with viewers that do not support JPEG Extended coding process (12-bit images). In this mode:

• ImageGear saves grayscale images as 8 bits per pixel, using "JPEG Baseline (Process 1)" transfer syntax. 
• ImageGear saves RGB images as 24 bits per pixel, using "JPEG Baseline (Process 1)" transfer syntax.

If the source image colorspace is different from RGB or grayscale, or the bit depth is greater, ImageGear automatically converts image rasters to one of the supported pixel formats on saving. See Pixel Format Conversion during Image Saving for more details.

As part of the JPEG Lossy compression process, ImageGear converts RGB rasters into YCbCr colorspace (or YCC in DICOM terminology) during saving. This conversion is fully encapsulated into the ImageGear JPEG codec; the application should not convert images to YCbCr before saving them to JPEG or DICOM JPEG.

To save an image as DICOM JPEG Baseline, use ImGearSavingFormats.DICOM saving format, and set SaveSyntax to ImGearDICOMTransferSyntaxes.JPEG_BASELINE_PR_1.

JPEG Lossless

In this mode:

• ImageGear saves grayscale images as 8-16 bits per pixel, using "JPEG Lossless, Non-Hierarchical (Process 14)" transfer syntax.
• ImageGear saves RGB images as 24 bits per pixel, using "JPEG Lossless, Non-Hierarchical (Process 14)" transfer syntax.

JPEG Lossless compression does not involve internal conversion or RGB rasters into YCbCr colorspace (YCC in DICOM terminology).

To save an image as DICOM JPEG Lossless, use ImGearSavingFormats.DICOM saving format, and set SaveSyntax to ImGearDICOMTransferSyntaxes.JPEG_LOSSLESS or ImGearDICOMTransferSyntaxes.JPEG_LOSSLESS_NONH_PR_14.

Saving DICOM Images Using RLE Compression

DICOM provides a mechanism for supporting the use of Run Length Encoding (RLE) Compression, which is a byte oriented lossless compression scheme.

• ImageGear saves grayscale images as 8-16 bits per pixel, using "RLE Lossless" transfer syntax. 
• ImageGear saves RGB images as 24 bits per pixel, using "RLE Lossless" transfer syntax.

If the source image color space is different from RGB or grayscale, or the bit depth is greater, ImageGear automatically converts image rasters to one of the supported pixel formats on saving. See Pixel Format Conversion during Image Saving for more details.

Use one of the following to save an image as DICOM RLE:

• Save the image as ImGearSavingFormats.DICOM_RLE (SaveSyntax parameter is ignored).
• Save the image as ImGearSavingFormats.DICOM and set SaveSyntax to ImGearDICOMTransferSyntaxes.RLE

Saving Non-DICOM Images to DICOM Format

ImageGear for Java allows saving of non-DICOM images to DICOM format. A default Secondary Capture DataSet is created for such images.

Saving Multiframe Images

The DICOM format is not designed for an easy insertion of pages. The following issues exist:

• Pages are stored sequentially rather than in arbitrary order. If the image is compressed, replacing a page requires rewriting all subsequent pages.
• "Number of pages" tag is stored as "Integer string". If, for example, tag is equal to "99", adding a page requires to increase length of this tag, and thus requires rewriting of the whole image.
• All pages in the file must have the same dimensions and compression.
• Some DICOM modalities support multiframe images, while others don't.

According to the above issues, DICOM format filter in ImageGear for Java has the following limitations:

• Only APPEND and OVERWRITE saving modes are supported (see ImGearSavingModes).
• ImageGear for Java allows appending a page to a DICOM file only if the file already has the "Number Of Pages" tag, and this tag has maximum possible length for an Integer String: 12 bytes.
• The page being saved must have the same dimensions and compression as existing pages in the file.
• ImageGear does not check if the image's modality allows multipage images.

If any of the limitations are encountered, ImageGear throws an exception.

To save a multipage image:

1. Load an image into an ImGearPage.
2. Save image to a new file (or use OVERWRITE mode).
3. Load the next image into an ImGearPage.
4. Save the image to the existing file, using APPEND mode.
5. Repeat steps 3 and 4 for all pages to be written.

Alternatively, create an ImGearDocument object, loading all images as ImGearPage objects in the document, and save the ImGearDocument as DICOM using the SaveDocument method.

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