View64 can be used to view native C64 image files without firing up an emulator with the respective editor.  For realistic display it supports PAL/NTSC display with scanlines, shadow masks and other artifacts.

• Open source, mostly portable C using SDL2
• Separate library for image decoding (libview64)
• Supports lot of image formats (70+)
• Some image formats are recognized without extensions
• PAL/NTSC S-Video and RGB rendering
• Scanline, shadow mask, chroma leakage simulation
• Multicolor interlace de-interlacing
• Hardware window scaling (where available)
• Image saving to BMP