ImGui + GLFW An example of runtime image generation

RuntimeImage.h

// An example of runtime image generation using Dear ImGui & GLFW
// c++ code by [email protected]
// Usage:
// RuntimeImage m_image;
// m_image.setSize(50, 50);
// m_image.setColor(255, 0, 255, 255);
// m_image.updateTexture();
// ImGui::Image((void*)(intptr_t)m_image.textureId(), m_image.imageSize());

#pragma once
#include <GLFW/glfw3.h>
#include <imgui.h>

class RuntimeImage
{
public:
    RuntimeImage() {
        setSize(50, 50);
        setColor(255, 0, 255, 255); // pink
    }

    void setSize(size_t vsize, size_t hsize)
    {
        if ((m_vsize != vsize) || (hsize != hsize)) {
            if (m_image != nullptr) delete m_image;
            m_image = new uint32_t[vsize * hsize];
            memset(m_image, 0, vsize * hsize * sizeof(uint32_t));
        }
        m_vsize = vsize;
        m_hsize = hsize;
    }
    
    void setColor(uint32_t red, uint32_t green, uint32_t blue, uint32_t alpha)
    {
        const uint32_t color = (alpha << 24) | (blue << 16) | (green << 8) | red;
        for (size_t i = 0; i != m_hsize * m_vsize; ++i) {
            m_image[i] = color;
        }
    }
  
    void updateTexture()
    {
        glBindTexture(GL_TEXTURE_2D, m_textureId);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, m_hsize, m_vsize, 0, GL_RGBA, GL_UNSIGNED_BYTE, (uint8_t*)m_image);
    }

    GLuint textureId() const { return m_textureId; }
    ImVec2 imageSize() const { return { float(m_vsize), float(m_hsize) }; }

private:
    GLuint m_textureId = 0;
    uint32_t* m_image = nullptr;
    GLsizei m_vsize = 0;
    GLsizei m_hsize = 0;
};