Image to C Array Converter (Arduino Bitmap)

Small displays on Arduino, ESP32 and other microcontrollers draw images from arrays in the program, not from files. This converter turns PNG, JPG, SVG or GIF images into C arrays in the layout your graphics library expects: 1-bit monochrome bitmaps for OLEDs (Adafruit GFX drawBitmap, the SSD1306 page layout, u8g2 XBM) or colour data for TFT screens (RGB565, RGB888, 8-bit grayscale). Resize, choose a threshold or dithering, invert, preview exactly what the display will show, and download a .h file. Images never leave your device.

How to use this tool

1. Choose one or more images.
2. Pick the output format your library uses (drawBitmap, SSD1306 buffer, drawXBM, RGB565…).
3. Set the display size, for example 128 × 64, and how to fit the image.
4. For 1-bit output adjust the threshold or pick dithering, and tick Invert for dark drawings on white.
5. Check the preview, then copy the code or download the .h file.

Formula

1-bit: bit = (0.299 R + 0.587 G + 0.114 B ≥ threshold) · RGB565 = (R & 0xF8) << 8 | (G & 0xFC) << 3 | B >> 3

Horizontal 1-bit rows are padded to whole bytes (MSB = leftmost pixel for Adafruit GFX, LSB for XBM). Vertical pages store 8 pixels of one column per byte, bit 0 at the top, as the SSD1306 does. Floyd–Steinberg spreads each pixel's error 7/16, 3/16, 5/16, 1/16 to its neighbours; Atkinson spreads 6/8 of it in eighths; Bayer compares each pixel with a 4 × 4 threshold matrix. Transparent areas are filled with the chosen background first.

Example

A 120 × 80 image with a blue background (#2563EB) and a yellow circle becomes, in RGB565, 9,600 values starting 0x231D — (32 << 8) | (96 << 3) | (235 >> 3) — or 19,200 bytes. As a 1-bit horizontal bitmap it is 15 bytes per row × 80 rows = 1,200 bytes: the blue (brightness 96) stays 0 and the circle (brightness 191) lights up, about 1,960 pixels.