• This application can convert .jpg, .jpeg, .png and .gif files with a size of max. 1 MB.
• After conversion it gives you back 2 output files: a .png file and a C64 .prg program file.
• The output .png file gives you an idea of the conversion result.
• The output .prg file contains the converted image as well and can display it on a C64.
• Download the .prg file and run it it on the C64 or an emulator. To exit the program and return to the BASIC prompt, press RUN/STOP + RESTORE simultaneously.
• Conversion mode:
  • Dithering: applies dithering, by combining different colors of the C64 palette, it gives the impression of another color.
  • Closest color: chooses per pixel of the original image the closest color available in the chosen palette and colors. Typically this results in rather ugly images.
• Palette:
  • Colodore: The palette consists of colors based on the Colodore model by Pepto, in particular it's based on the most common hardware revision seen for the PAL VIC II chip. This gives a more realistic impression of how a picture can look like on a real C64. Sliders can be used to further tweak the colors.
  • Saturated: The palette consists of saturated colors (taken from C64-Wiki). This was the only and default palette in use prior to V6 of the tool.
  The chosen palette affects how the dithering algorithm tries to approximate the colors in the original image.
• Sliders:
  The brightness, contrast and saturation slider are only available when the Colodore model is used as palette. They allow tweaking the color palette which is then further used for the color approximation. The three sliders range from 0 to 100. The default values are 50, 100 and 50 for respectively brightness, contrast and saturation. Note that using extreme settings, the difference between the .png and the .prg file may be huge. The .png file uses the modified colors to generate an impression. The .prg will only result in a similar view if the emulator or the CRT you are using has similar brighness, contrast and saturation settings.
• Colors:
  • All colors: all the 16 colors of the C64 are used.
  • RGB: Black, white, red, green and blue colors are used.
  • Black/white: only black and white are used.
  • Greyscale: Black, white and the 3 greys of the C64 palette are used.
  • Custom: Custom choice of 2 up to 16 colors of the C64 palette.
• Resizing mode:
  • Fitted: If the original image has a different width/height ratio than supported by the C64 graphics mode, the application will fit the complete image while keeping the correct ratio by either adding black borders to the left and right sides or the top and bottom sides of the original image. Fine tune this mode further with the Aspect ratio option.
  • Cropped: If the original image has a different width/height ratio than supported by the C64 graphics mode, the application will use the maximum possible screen space with the correct ratio by cropping the original image. The center of the image is kept, by either cropping the left and right sides or the top and bottom sides. Fine tune this mode further with the Aspect ratio option.
  • Stretched: In this mode the original image is stretched so that it gets displayed entirely and will fill the whole screen. Orginal images that deviates too much from the ideal ratio, will look distorted. The image will not be cropped, neither borders will be added. In this mode the Aspect ratio option has only effect on the generated .png image and not on the C64 program.
• Aspect ratio:
  • Original: The used aspect ratio is 8:5. The resulting C64 .prg may not look fine, especially on the NTSC version of the C64. A circle will ook rather like an ellips.
  • PAL: Conversion is optimized to show the image on a PAL version of the C64.
  • NTSC: Conversion is optimized to show the image on a NTSC version of the C64.

• C64 Multicolor Bitmap Mode
• A picture consists of 1 medium resolution bitmap of size 160 x 200 pixels, with a Pixel Aspect Ratio of 2:1.
• This is an effective bitmap of 160x200 pixels, expanded by a factor 2 in the horizontal direction when rendered by a C64 (resulting in a 320x200 picture.
• 1 background color.
• Max 3 additional colors per character block of 8x8 pixels (after the expansion).
• C64 has only a palette of 16 fixed colors.
• Due to the above limitations of the C64, artefacts are likely be visible in the converted image.
• No sprites used.
• The resulting .png file tries in no way to look like an image from a CRT. Real CRT artefacts like scanlines and Hanover bars are not implemented.
• Future development:
  • Slide show of max 4 images?
  • Hires converter?
  • Fli converter?
  • ...

A picture of a lighthouse is converted with different settings. The aspect ratio is in all cases the 'Original' one. Depending on the settings the result is more or less appealing. This depends also also on the level of detail and different colors of the original image. You may need to play around with the different settings.

Original image

Dithering, Colodore, All colors

Dithering, Saturated, All colors

Closest color, Saturated, Full color

Dithering, Saturated, Greyscale

Dithering, Saturated, Black/white

Closest color, Saturated, RGB

Dithering, Saturated, Custom (Black, White, Yellow, Violet, Cyan)

A picture of the C64 logo is converted with different settings. The aspect ratio is in all cases the 'Original' one. The second picture shows the conversion using the Colodore model with default settings for brightness, contrast and saturation. It shows that the white color of the 'chicken lips' tends to bleed into the black background. In the third picture the brightness parameter was increased from 50 to 70, resulting in less color bleeding and a more appealing result.

Original image

Colodore b:50, c: 100, s:50

Colodore b:70, c: 100, s:50

• V8 - 2024, Nov 13:
  • The border color is now always black.
  • The resulting C64 .prg file is 450 bytes smaller and the execution is 1.5 times faster (though you can't really see that).
• V7 - 2024, Oct 28:
  • Add the brightness, contrast and saturation sliders to fine tune the Colodore palette.
  • Add a new example demonstrating the effect the sliders.
• V6 - 2024, Oct 13:
  • Add option to choose between a saturated and the Colodore palette.
  • Style the parameter buttons of UI more like the C64 theme.
• V5 - 2022, Dec 28:
  • Add option to fit the image into the screen by adding borders.
• V4 - 2022, Dec 24:
  • Add option to stretch the image over the whole screen.
• V3 - 2022, Sept 11:
  • Add option to choose a custom set of colors to do the conversion with.
• V2 - 2022, Sept 1:
  • Minor bugfix, not affecting the output results.
  • Speed up of the conversion.
  • Additional help information.
• V1 - 2018, Sept 1:
  • Initial release of the img2c64mc online tool.