PPM to PAL Converter

PAL is a 16-bit per pixel interleaved YUV image format that stores color information using a luminance-chrominance model rather than direct RGB values. Each pixel pair is packed into four bytes using the UYVY byte ordering — U (Cb), Y0, V (Cr), Y1 — where two adjacent pixels share a single set of chroma (color difference) samples while each retaining its own luminance (brightness) value. This 4:2:2 chroma subsampling halves the color resolution horizontally with negligible perceptual impact, since human vision is far more sensitive to brightness variations than color detail. The format traces its conceptual roots to analog broadcast television standards developed during the 1960s and 1970s, where separating luminance and chrominance enabled backward-compatible color transmission alongside existing monochrome signals. In digital imaging, 16-bit YUV serves as a common intermediate representation for video capture hardware, frame grabbers, and image processing pipelines that work in the YCbCr color space internally before converting to RGB for display. One advantage is bandwidth efficiency: at 16 bits per pixel, UYVY requires roughly two-thirds the data of uncompressed 24-bit RGB while preserving virtually identical perceived quality, making it well suited for high-throughput video capture and real-time image processing applications. The format's direct correspondence to how video hardware captures and outputs data provides another practical benefit — many capture cards and camera sensors natively produce UYVY data, so storing it in PAL form avoids an unnecessary color space conversion step that would add latency and introduce rounding artifacts.