Image Box

An Image Box displays images in GIF, JPEG, PNG, BMP, WBMP, PDF, and SVG formats.

Image Box (ImageBox type) is a layout container, found in the Drawable group in the Tool Box view.

The images are cached on a per document basis. The default resolution is the current screen resolution.

Note: The Image Box renders only the first page of a PDF document. If you want to embed the entire PDF, use the PDF Box.

Properties

Select the object on the Report Design page to display its properties in the Properties View.

These properties are specific to Image Box:

Location, Intended Resolution, Fill

Use the Location property to specify the location of the image to be rendered.

If you want to preserve the aspect ratio of an image, set the value of either length (y-size) or width (x-size), allowing Report Writer to calculate the corresponding value. If you set both properties, the resulting image appears distorted.

Note: Beginning with version 2.4x, the tile property is replaced by a new property, fill. If you open a document containing the tile property, it is automatically replaced by fill.

Embedding images

To embed a resource, use the "data" URL type, which allows the data to be encoded in the body of the URL text. The full syntax of data URLs is:

data:[<MIME-type>][;charset=<encoding>][;base64],<data>

See data URI scheme (Wikipedia link) for a complete description of the concept and the syntax.

For our purposes, it is sufficient to support a simplified subset that omits the charset and assumes that characters are encoded in UTF-8. Image data is always encoded in base64 (Wikipedia link) while other data such as HTML content is typically “Percent encoded” (Wikipedia link).

For images, the simplified URL has the form "data:/text:xxx;base64,<data>" where xxx is one of “png”, “jpg”, “gif” or “bmp”. For an image, the syntax is:
data:image/png;base64, followed by the base 64 encoded bitmap data of the image

To automatically construct this URL, click the ... button for the Location property. Choose the file and select the Embed in document check box.

Figure: Embed in document checkbox


This figure is a screenshot showing the Embed in document checkbox.

Populating images from blob variables

If you drag a BYTE variable from the Data View onto the Report Design, an Image Box object is created and the Location property is filled with this formula: 
data:image/jpg;base64,"+imageblob
where imageblob is the name of the blob

You can also enter the blob variable name using the Expression Editor for the Location property:

Figure: Entering blob variable name in RTL Expression editor


This figure is a screenshot of entering a blob variable name in an RTL Expression: "data:image/jpg;base64,"+imageblob.
Note: Since a blob variable may contain images of various types, the implementation ignores the image type declared in the formula and looks at the encoded data to determine the image type. This formula also works for blobs of png type.

SVG images

Using SVG images instead of bitmap images can substantially reduce the document size. When providing the SVG content from a 4GL variable, use the mime type image/svg so that the url looks something like data:image/svg,... when read from a string variable and data:image/svg;base64,... when read from a BLOB. The currently supported SVG version is "1.2 Tiny" (See http://www.w3.org/TR/SVGTiny12).

Fallback image

A fallback image is displayed if the requested image is not found. To specify a fallback image, set the GRE_DEFAULT_IMAGE_URL environment variable to the image URL. The image URL can be a relative URL, which resolves relative to the location of the form design (4rp) file.