PPM to PCD Converter

PCD (Photo CD) is a proprietary image format developed by Eastman Kodak in partnership with Philips, launched in 1992 as a system for transferring 35mm film photographs to compact discs for digital viewing and printing. Each PCD file stores a single photograph at five different resolutions in a hierarchical structure called an Image Pac: Base/16 (192x128), Base/4 (384x256), Base (768x512), 4Base (1536x1024), and 16Base (3072x2048), with optional 64Base (6144x4096) on Pro Photo CD discs. Images are stored in Kodak's proprietary YCC color space (a variant of CIE Lab via the Photo YCC color model), which captures a wider gamut than sRGB, at 8 bits per component in the luminance channel and subsampled chrominance. The multi-resolution pyramid is encoded using a progressive scheme: the Base image is stored directly, and each higher resolution is stored as a residual (difference) that refines the upscaled previous level, keeping the total file size manageable. One advantage is the exceptional scan quality: Photo CD scans were performed on Kodak's professional PIW (Photo Imaging Workstation) scanners by trained operators, producing consistently excellent results from 35mm negatives and slides — often better than what contemporary consumer flatbed scanners could achieve. The multi-resolution structure is another notable feature: a single PCD file serves needs from thumbnail browsing to high-resolution printing without separate file versions. PCD files can be read by Adobe Photoshop, ImageMagick, GIMP (via plugin), IrfanView, and XnView, ensuring continued access to the millions of Photo CD images created during the format's commercial peak in the 1990s.