BMPImageCreator

• A simple C++ library to generate BMP images with basic drawing primitives and bitmap-font text rendering.

• If you get the fatal error "font file not found", check Debugging.

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Features

• Draw pixels, lines, rectangles (filled or outlined), and circles (filled or outlined).
• Load and render a cropped 8×8 monochrome font from a .fnt file with scaling and word wrap.
• Automatic clipping of out-of-bounds pixels.
• Pure C++17: no external dependencies beyond the standard library.

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API Reference

Function	Description
BMPImageCreator(int32_t width, int32_t height)	Allocate canvas and initialize BMP headers (24-bit color).
void setDefaultPixelRGB(int r, int g, int b)	Fill entire canvas with a solid RGB color (clamped 0–255).
void setPixel(int x, int y, int r, int g, int b)	Set a single pixel at (x,y); ignores out-of-bounds and clamps color.
void drawRectangle(int x0,int y0,int x1,int y1,int r,int g,int b,bool fill)	Draw a filled or outlined rectangle; swaps coords internally.
void drawLine(int x0,int y0,int x1,int y1,int r,int g,int b)	Draw a line using Bresenham’s algorithm.
void drawCircle(int cx,int cy,int radius,int r,int g,int b,bool fill)	Draw a circle using the Midpoint algorithm (filled or outline).
bool loadFont(const std::string &filename)	Load and crop a bitpacked 8×8 .fnt font with 128 glyphs.
void drawText(int x,int y,const std::string &text,int r,int g,int b,int scale,bool wrap)	Render ASCII text with scaling and word-wrap.
void saveFile(const std::string &filename) const	Write the canvas to <filename>.bmp (BGR, bottom-up rows).

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Project Structure

src/
 ├─ bmp_image_creator.cpp
 ├─ bmp_image_creator.h
 └─ font.fnt
example/
 ├─ example.cpp
 └─ output_image.bmp
legacy/
 └─ bmp_image_creator_legacy.cpp
.gitignore
Makefile
README
LICENSE

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How to Run

1. Open a terminal and navigate to the project root directory.

2. Build the example app:

   make

3. Run the example:

   make run

4. Output: The program generates output_image.bmp.

Build without Make

From the project root, you can compile and run directly with g++:

g++ -std=c++17 -O2 -Wall -Wextra -pedantic \
    example/example.cpp src/bmp_image_creator.cpp \
    -o example/example_app

./example/example_app

Note: Run from the repository root so src/font.fnt is found by the program. If you run from a different working directory, update the font path in src/bmp_image_creator.h or adjust your working directory.

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If you encounter a "font file not found" error, see Debugging for instructions on setting the correct font path.

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Debugging

• If you the program can't find the font (throws an error), change the font path in the header file to the font file location (based on where you're compiling from).

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Usage

#include "../src/bmp_image_creator.h"

int main() {

    // Example usage of BMPImageCreator
    BMPImageCreator bmp(100, 100);

    // Set default pixel color to red
    bmp.setDefaultPixelRGB(255, 0, 0); 

    // Draw a filled green rectangle
    bmp.drawRectangle(10, 10, 90, 90, 0, 255, 0, true); 

    // Draw a blue line
    bmp.drawLine(10, 10, 90, 90, 0, 0, 255); 

    // Draw a yellow circle outline
    bmp.drawCircle(50, 50, 30, 255, 255, 0, false);  

    // Black wrapped text
    bmp.drawText(10, 10, "Hello,\nBMP world!", 0, 0, 0, 1, true);

    // Save the BMP image to a file
    bmp.saveFile("output_image"); 

    return 0;
}

Font

• Font from darkrose (https://opengameart.org/content/8x8-ascii-bitmap-font-with-c-source) (modified, converted to .fnt (bit images of each character) and cropped)

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License

• Everyone is free to use, modify, and distribute this code for any purpose, with or without attribution.
• For more info, refer to the license.