TIEVisionImage.normalizeBackground

Declaration

function normalizeBackground(tileSize: int32_t = 16; backgroundValue: int32_t = 200): TIEVisionImage; safecall;

Description

Flattens uneven lighting (via Leptonica). The background brightness is estimated across the image (using a grayscale closing, which removes the text) and every pixel is rescaled so the background becomes a uniform value, while text keeps its contrast. This also works where the background itself is dark, such as the unlit side of a photographed page.
Useful for photos of documents, vignetting, yellowed paper and shadows. After normalization even a simple global threshold often works well.
Returns a new image: 8-bit gray for gray or 1-bit images, otherwise 24-bit color (any alpha channel is discarded). The current image is not changed. Images smaller than 8 x 8 pixels are returned unchanged.

Demo

Example

img := ImageEnView1.IEBitmap.GetIEVisionImage().normalizeBackground();
ImageEnView1.IEBitmap.AssignIEVisionImage( img );
ImageEnView1.Update();

See Also

◼prepareForOCR
◼clahe

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