Handling Alpha Transparency in PNG Graphics
PNG graphics often contain transparent backgrounds. In standard OCR engines, transparency is interpreted as black, turning black text invisible. Our PNG pipeline flattens alpha channels onto pure white to maintain crisp character contrast.
PNG Use Cases: Web Graphics, Diagrams, and UI Mockups
PNG is the default format for web screenshots, flowchart exports, UI wireframes, and diagram tools like Figma, Lucidchart, and Draw.io. These images typically contain clean vector-rendered text at screen resolution (72 to 144 DPI). Because PNG uses lossless compression, letter edges remain sharp without the blocking artifacts found in JPEG files. This makes PNG one of the most OCR-friendly image formats available. The converter handles both small icon-sized crops and full-page diagram exports without manual resizing.
Color Depth and Bit-Depth Handling
PNG files support 8-bit, 24-bit, and 32-bit color depths. Our preprocessing pipeline normalizes all variants to 8-bit grayscale before binarization. For 32-bit RGBA images, the alpha channel is composited onto white first. Indexed-color PNGs (8-bit palette mode) are expanded to full grayscale to avoid palette quantization errors during thresholding. This normalization step ensures consistent recognition accuracy regardless of how the PNG was originally exported.