`ImGui::Image()` doesn't load the given Image.

[MubinMuhammad]

Version/Branch of Dear ImGui:

Version 1.91.5, Branch: master

Back-ends:

imgui_impl_glfw.cpp + imgui_impl_opengl3.cpp

Compiler, OS:

archlinux 6.6.56-1-lts + g++ 14.2.1

Full config/build information:

Used a python script to build the project.

Details:

Before the details, I did read Image Loading and Displaying Examples from ImGui Wiki. As I'm using OpenGL, the general steps are:

• use a image read/write library. In my case, I used libimago
• create texture id and bind it.
• configure glTexParameteri.
• send the texture to GPU.
• unbind the texture id.
• return id.

For this, I created this function:

unsigned int engine::textureInit(const img_pixmap &img) {
    GLuint texture_id;
    glGenTextures(1, &texture_id);
    glBindTexture(GL_TEXTURE_2D, texture_id);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

    glTexImage2D(GL_TEXTURE_2D, 0,
                 img.pixelsz == 3 ? GL_RGB : GL_RGBA,
                 img.width, img.height, 0,
                 img.pixelsz == 3 ? GL_RGB : GL_RGBA,
                 GL_UNSIGNED_BYTE, (unsigned char *)img.pixels);

    glBindTexture(GL_TEXTURE_2D, 0);

    return texture_id;
}

The next step is to just use ImGui::Image() to render the image to a window. Here is the function I wrote for this:

void app::Image::show() {
    glBindTexture(GL_TEXTURE_2D, m_id); // m_id is the texture id
    ImGui::Begin(m_name.c_str()); // m_name is the image path
    ImGui::Text("pointer: %x\nsize: %dx%d", m_id,
                m_pix_map.width, m_pix_map.height); // m_pix_map is img_pixmap by `libimago`
    ImGui::Image((intptr_t)m_id, (ImVec2){256, 256});
    ImGui::End();
    glBindTexture(GL_TEXTURE_2D, 0);
}

After all of this I don't get the Image I select. Instead, I get a Font Texture Atlas. This happens no matter which image I choose.

Screenshots/Video:

No matter which Image I choose, I always find this texture atlas:

Minimal, Complete and Verifiable Example code:

Example code is given in the details.

[ocornut]

Well have you checked what’s your value of m_id ? It is valid ? Use a debugger and confirm all the values and state from both functions.

There’s no need to call glBindTexture() while submitting imgui calls.

[MubinMuhammad]

How do I check the validity of m_id? The Image init function is:

bool app::Image::init(const char *path) {
    img_init(&m_pix_map);
    img_load(&m_pix_map, path);

    if (m_pix_map.fmt == NUM_IMG_FMT) {
        return false;
    }

    m_name = path;
    m_id = engine::textureInit(m_pix_map);
    return true;
}

Here, if the image is invalid the function returns false. But as it doesn't return false, that means the image is valid. And yet, it shows the texture atlas.

Also, the provided image shows pointer: 2 does it confirm validity? Thanks.

[MubinMuhammad]

The actual issue was on my part, and doesn't relate with this. Closing.