Monkeybread Software - DynaPDF Manual

DynaPDF Manual - Page 640

Function Reference

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The function must be called within an open page and with the same Flags which were used in the

RenderPage() or RenderPageEx() call. The flags to exclude annotations or form fields from

rendering will be ignored.

To render the annotations and fields from a page, open the wished page with EditPage() and call

GetPageAnnotCount(). Now you can loop over the annotations from 0 to GetPageAnnotCount() - 1

with GetPageAnnotEx(). A form field is an annotation of the type atWidget.

The member StructSize of the structure TPDFBitmap must be set to sizeof(TPDFBitmap) before the

function can be called.

The members DestX, DestY define the destination position on the rendered page image. The position

is returned in top down coordinates and measured in pixels. Note that annotations and form fields

can occur outside the visible area of a page.

If the coordinates of the page were translated, this is the case if the x or y members of the matrix

were non-zero when rendering the page, then this offset must be added to the returned destination

coordinates:

out.DestX += (SI32)img.Matrix.x;

out.DestY += (SI32)img.Matrix.y;

Since the matrix is already defined in device coordinates, no further math is required to calculate the

correct destination position.

Note that annotations and form fields can contain transparent areas. The pixel format should

contain an alpha channel so that it can be correctly blended on the page image.

The Button State (parameter State)

Only form fields support different appearance states. Annotations use always the up state. If no

appearance stream is defined for a specific state then the normal appearance will be returned. Check

boxes contain mostly four different appearance streams: two for the up state and two for the down

state. The function selects the appearance stream for a specific state depending on the field value.

Therefore, all four appearances can only be rendered, if the field value will be changed from

checked to unchecked or vice versa.

Raw image output

By default, annotations or form fields are rendered into a raw memory buffer that is returned in the

TPDFBitmap structure. The image buffer can be released with FreeImageBuffer() when it is no

longer needed. It is not required to release the image buffer every time before the next annotation or

field can be rendered but previously returned pointers become invalid once the next image was

rendered. After the last annotation was rendered, the image buffer should be released with

FreeImageBuffer().

Note that the return value of the function must be zero, otherwise no image will be returned. See

Return values at the end of the function description.