Color inversion

When working with white (or light) text on a black (or other dark) background, recognition accuracy may suffer. It can be greatly improved by reversing the colors of the image so that light areas appear dark and dark areas appear light. In addition, other colors are also swapped: red becomes cyan, green becomes magenta, blue becomes yellow, and so on.

Aspose.OCR for Python via .NET provides the automated processing filter that inverts colors in the image before proceeding to recognition.

Inverting image colors

To automatically invert colors in an image before recognition, run the image through invert processing filter.

# Instantiate Aspose.OCR API
api = AsposeOcr()
# Initialize image processing
filters = PreprocessingFilter()
filters.add(PreprocessingFilter.invert())
# Add image to the recognition batch and apply processing filter
input = OcrInput(InputType.SINGLE_IMAGE, filters)
input.add("source.png")
# Save processed image to the "result" folder
ImageProcessing.save(input, "result")
# Recognize the image
result = api.recognize(input)
# Print recognition result
print(result[0].recognition_text)

Usage scenarios

Automatic color inversion is recommended for the following images:

• White text on black (dark) background.
• Advertisements.
• Business cards.
• Screenshots.