DICOM PS3.3 2021d - Information Object Definitions

C.10.4 Displayed Area Module (Current)
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### C.10.4 Displayed Area Module

This Module describes Attributes required to define a Specified Displayed Area space.

The Specified Displayed Area is that portion of the image displayed on the device.

If Presentation Size Mode (0070,0100) is specified as SCALE TO FIT, then the specified area shall be displayed as large as possible within the available area on the display or window, i.e., magnified or minified if necessary to fit the display or window space available.

If Presentation Size Mode (0070,0100) is specified as TRUE SIZE, then the physical size of the rendered image pixels shall be the same on the screen as specified in Presentation Pixel Spacing (0070,0101).

If Presentation Size Mode (0070,0100) is specified as MAGNIFY, then the factor that shall be used to spatially interpolate image pixels to create pixels on the display is defined.

### Note

If this factor is specified as 1.0, then one image pixel will correspond to one displayed pixel, and if the Specified Displayed Area is the entire image, and it fits on the display, then the number of displayed pixels will equal the number of image pixels.

In all modes, the actual area rendered on a display device may be greater than the Specified Display Area, if the ratio of rows and columns of the Specified Display Area differs from the ratio of rows and columns of the display device or window. The Displayed Area relative annotations specified in Section C.10.5 Graphic Annotation Module are rendered relative to the Specified Displayed Area, not the actual rendered displayed area.

### Note

1. The content of a display outside the Specified Display Area is not defined. In particular no padding value (such as black) is specified.

2. In the TRUE SIZE and MAGNIFY modes, if the entire Specified Displayed Area is not visible, then display relative graphic annotations may be obscured.

This Module explicitly specifies the aspect ratio to be used to display the image, even if it is 1:1, and it may be different from that specified in the referenced image.

### Note

1. Depending on the mode, the aspect ratio is either specified using the Presentation Pixel Aspect Ratio (0070,0102), or derived from the Presentation Pixel Spacing (0070,0101).

2. This explicit definition of aspect ratio implies that graphic objects that are specified relative to the Specified Display Area will not change their shape regardless of the size or shape of the presentation device (e.g., whether a landscape or portrait monitor is used).

3. The mechanism of interpolation, if necessary, is not specified.

4. The image may need to be cropped and scroll bars or a panning mechanism provided in order to provide access to sections of the image that do not fit within the available area on the display or window.

Table C.10-4. Displayed Area Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Displayed Area Selection Sequence | (0070,005A) | 1 | A Sequence of Items each of which describes the displayed area selection for a group of images or frames. Sufficient Items shall be present to describe every image and frame listed in the Presentation State Relationship Module. One or more Items shall be included in this Sequence.
>Referenced Image Sequence | (0008,1140) | 1C | The subset of images and frames listed in the Presentation State Relationship Module, to which this displayed area selection applies. One or more Items shall be included in this Sequence. Required if the displayed area selection in this Item does not apply to all the images and frames listed in the Presentation State Relationship Module.
>>Include Table 10-3 “Image SOP Instance Reference Macro Attributes” |
>Pixel Origin Interpretation | (0048,0301) | 1C | For a referenced multi-frame image, specifies whether the Displayed Area Top Left Hand Corner (0070,0052) and Displayed Area Bottom Right Hand Corner (0070,0053) are to be interpreted relative to the individual frame pixel origins, or relative to the Total Pixel Matrix origin (see Section C.8.12.4.1.4). Required if the value of Referenced SOP Class UID (0008,1150) within Referenced Image Sequence (0008,1140) is 1.2.840.10008.5.1.4.1.1.77.1.6 (VL Whole Slide Microscopy Image). May be present otherwise. Enumerated Values: FRAME relative to individual frame VOLUME relative to Total Image Matrix If not present, TLHC and BRHC are defined relative to the frame pixel origins.
>Displayed Area Top Left Hand Corner | (0070,0052) | 1 | The top left (after spatial transformation) pixel in the referenced image to be displayed, given as column\row. Column is the horizontal (before spatial transformation) offset (X) and row is the vertical (before spatial transformation) offset (Y) relative to the origin of the pixel data before spatial transformation, which is 1\1. See Figure C.10.4-1.
>Displayed Area Bottom Right Hand Corner | (0070,0053) | 1 | The bottom right (after spatial transformation) pixel in the referenced image to be displayed, given as column\row. Column is the horizontal (before spatial transformation) offset (X) and row is the vertical (before spatial transformation) offset (Y) relative to the origin of the pixel data before spatial transformation, which is 1\1. See Figure C.10.4-1.
>Presentation Size Mode | (0070,0100) | 1 | Manner of selection of display size. Enumerated Values: SCALE TO FIT TRUE SIZE MAGNIFY See Section C.10.4 for further explanation.
>Presentation Pixel Spacing | (0070,0101) | 1C | Physical distance between the center of each pixel in the referenced image (before spatial transformation), specified by a numeric pair - adjacent row spacing (delimiter) adjacent column spacing in mm. See Section 10.7.1.3 for further explanation of the value order. ### Note This value may be different from Pixel Spacing (0028,0030) or Imager Pixel Spacing (0018,1164) specified in the referenced image, which are ignored, since some form of calibration may have been performed (for example by reference to an object of known size in the image). If the row and column spacing are different, then the pixel aspect ratio of the image is not 1:1. Required if Presentation Size Mode (0070,0100) is TRUE SIZE, in which case the values will correspond to the physical distance between the center of each pixel on the display device. May be present if Presentation Size Mode (0070,0100) is SCALE TO FIT or MAGNIFY, in which case the values are used to compute the aspect ratio of the image pixels.
>Presentation Pixel Aspect Ratio | (0070,0102) | 1C | Ratio of the vertical size and the horizontal size of the pixels in the referenced image, to be used to display the referenced image, specified by a pair of integer values where the first value is the vertical pixel size and the second value is the horizontal pixel size. See Section C.7.6.3.1.7. Required if Presentation Pixel Spacing (0070,0101) is not present. ### Note This value may be different from the aspect ratio specified by Pixel Aspect Ratio (0028,0034) in the referenced image, or implied by the values of Pixel Spacing (0028,0030) or Imager Pixel Spacing (0018,1164) specified in the referenced image, which are ignored. This value must be specified even if the aspect ratio is 1:1.
>Presentation Pixel Magnification Ratio | (0070,0103) | 1C | Ratio of displayed pixels to source pixels, specified in one dimension. Required if Presentation Size Mode (0070,0100) is MAGNIFY. ### Note A value of 1.0 would imply that one pixel in the referenced image would be displayed as one pixel on the display (i.e., it would not be interpolated if the aspect ratio of the image pixels is 1:1). A value of 2.0 would imply that one pixel in the referenced image would be displayed as 4 pixels on the display (i.e., up-sampled by a factor of 2 in each of the row and column directions). A value of 0.5 would imply that 4 pixels in the referenced image would be displayed as 1 pixel on the display (i.e., down-sampled by a factor of 2 in each of the row and column directions). If the source pixels have an aspect ratio of other than 1:1, then they are assumed to have been interpolated to a display pixel aspect ratio of 1:1 prior to magnification.

### Note

1. In scale to fit mode, the Displayed Area Top Left Hand Corner (TLHC) and Bottom Right Hand Corner (BRHC) have the effect of defining how any zoom or magnification and/or pan has been applied to select a region of an image to be displayed (the Specified Displayed Area), without assuming anything about the size of the actual display.

2. The TLHC and BRHC may be outside the boundaries of the image pixel data (e.g., the TLHC may be 0 or negative, or the BRHC may be greater than Rows or Columns), allowing minification or placement of the image pixel data within a larger Specified Displayed Area. There is no provision to position a zoomed selected sub-area of the image pixel data within a larger Specified Displayed Area.

3. When Pixel Origin Interpretation (0048,0301) value is VOLUME, the selected Display Area may extend across multiple frames, and may include pixel locations for which there is no pixel data (outside the edge of the imaged volume, not encoded in a sparse encoding, or not within explicitly selected frames).

Figure C.10.4-1. Example of Displayed Area Selection Addressing of Pixels Before and After Spatial Transformation

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DICOM PS3.3 2021d - Information Object Definitions