This repo has been moved to Gitlab and is no longer maintained here.

text_on_image

A small header file that helps you write text on images. It supports:

• Letters (upper/lowercase)
• Numbers
• Spaces.

Does not support any symbols.

It could be helpful for debugging and stuff. It uses stb_image_resize under the hood to get you the desired size of text.

Usage

• Needs c++14 or newer.
• Drop the rdi_text_on_image.h into your project and include it.
• You must define RDI_TEXT_ON_IMAGE_IMPLEMENTATION somewhere before you include it.

nuff talking, let's learn with an example:

#define STB_IMAGE_IMPLEMENTATION
#define STB_IMAGE_WRITE_IMPLEMENTATION
#include "stb_image.h"
#include "stb_image_write.h"

#define RDI_TEXT_ON_IMAGE_IMPLEMENTATION
#include "rdi_text_on_image.h"

int main()
{
  int height, width, channels;
  std::uint8_t* image_data = stbi_load("../test/kitten_png_image.png", &width, &height, &channels, 0);

  RDI::Public::Image image{
	image_data, // pixels array
	(size_t)channels, // number of channels
	(size_t)width, // input image width
	(size_t)height // input image height
  };

  RDI::Public::Text text{
	"Here are some text and numbers 5539", // text you'd like to display
	42, // size
	100, // x coordinate
	100 // y coordinate as to where you'd like the text to be displayed on the image
  };

  // WARNING: this function changes the pixels in the image that you've passed
  RDI::Public::write_text_on_image(image, text);

  stbi_write_png("../kitten_png_image.png", width, height, channels, image_data, 0);

  stbi_image_free(image_data);
}

I'm using stb_image to load the image. Maybe you use something else, that's okay but the byte stream needs to be a one dimentional array of char or std::uint8_t in the form of rgbrgbrgb... etc where r, g and b are red, green and blue 0 to 255 values respectively. or if it's a single channel then ppppp... where p is the pixel value from 0 to 255.

WARNING

RDI::Public::write_text_on_image changes the pixels in the image that you've passed. If you'd like to preserve the original image, take a copy before sending it to this function.

Contributing

Well you'll have to understand the code.

• The first part of the header are decalaration.
• And then there is the implementation of stb_image_resize (I copied the whole thing and pasted it in).
• After that you'll find a map called char_to_pixels which as the name implies, maps each character to the pixels that form it.
• There's the make_text_overlay function which takes the text and creates an image overlay out of it using the char_to_pixels map.
• lastly write_text_on_image which the user actually calls. It basically calls make_text_overlay, resizes the text_overlay image and then applies it.