Every image based multimedia record in EMu has a table of resolutions associated with it. The Resolutions table contains one entry per image format / size maintained and appears on the Resolutions tab in the Multimedia module:
For each image the following properties are kept:
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Identifier
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The name of the file that contains the image in the Multimedia repository.
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Width (pixels)
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The width of the image in pixels.
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Height (pixels)
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The height of the image in pixels.
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Bits/Pixel
Colour Depth
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The number of bits used to represent one pixel in the image. This may also be known as the Colour Depth.
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Planes
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The number of layers used to form the image. Some image formats (e.g. TIFF) split an image up into layers (e.g. one layer per primary colour).
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Colours
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The maximum number of colours that may be represented in an image. For non-palette based formats (e.g. JPEG) this is directly related to the Bits/Pixel. For palette based formats (e.g. GIF) the number of colours is the number of palette entries allocated.
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Images
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The number of images stored within the image file. Some image formats (e.g. TIFF) allow multiple pages to be stored within the one image file.
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Compression
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The type of compression used to store the image data. Most image formats are tied to their corresponding internal compression format, but TIFF supports many compression types.
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File Size (bytes)
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The size of the image file in bytes.
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Quality
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The compression quality for jpeg images. A value between 100 and 1 is allowed, where 100 is lossless compression and 1 very lossy compression.
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MIME Type
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The Multipurpose Internet Mail Extensions document type. The value image will be set for all image media.
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MIME Format
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The format of the image. Possible values include gif, png, jpeg, tiff, etc.
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As the Identifier, File Size, MIME Type and MIME Format properties are determined by the System, they cannot be modified. All other attributes may be modified; however the System will provide initial values as determined by the image.
The name of each image follows a certain format. The format is basename.size.format
where:
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basename
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is the name of the original image file minus the file extension.
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size
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is the generated image size (note this is not necessarily the same as the image width and height).
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format
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is the file extension for the given image format.
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There are two exceptions to this naming convention:
- The original image. This is always the first entry listed in the Resolutions table and it excludes the size component.
- The thumbnail image. This is the second entry in the Resolutions table and has a size component of thumb.
The size component does not reflect the image width and height, but rather indicates the resolution used to generate the image. For example, if an image is 200x100 pixels and a 100x100 image is generated from it while still maintaining the aspect ratio, the generated image will be 100x50 pixels. The size component will be 100x100, even though the image is only 100x50 pixels.
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