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Asked: 2025-05-17T22:14:13+05:30

How can I modify my code to successfully load and render 8-bit BMP images using D3DXCreateTextureFromFileInMemoryEx?

I’ve been working on a project that involves rendering various image types using DirectX 9, and I’ve hit a bit of a wall with 8-bit BMP images. My `LoadTexture` function works like a charm for most formats, but it seems to choke whenever it tries to process these specific 8-bit BMP files.

Here’s a snippet of my rendering function if that helps you visualize what I’m working with:

“`cpp
void LoadTexture(const std::vector& img, ImTextureID* mytexture) {
if (img.empty() || !oTexture)
return;

IDirect3DTexture9* m_texture = nullptr;
D3DXIMAGE_INFO d3xinfo = { 0 };

HRESULT hr = D3DXCreateTextureFromFileInMemoryEx(
MyDX9::pDevice,
img.data(),
static_cast(img.size()),
D3DX_DEFAULT_NONPOW2,
D3DX_DEFAULT_NONPOW2,
D3DX_DEFAULT,
0,
D3DFMT_UNKNOWN,
D3DPOOL_DEFAULT,
D3DX_DEFAULT,
D3DX_DEFAULT,
0,
&d3xinfo,
nullptr,
&m_texture
);

if (FAILED(hr))
return;

*mytexture = reinterpret_cast(m_texture);
}
“`

The function does its job well for most standard image formats, but 8-bit BMP images just won’t load. I’ve tried tweaking a few parameters in `D3DXCreateTextureFromFileInMemoryEx`, but I can’t seem to make any progress.

I’ve also wondered if the problem might stem from how 8-bit BMP files handle color palettes or the format specifier within the function since I’m currently using `D3DFMT_UNKNOWN`. Should I be explicitly specifying a format that accommodates 8-bit BMPs?

Is there something specific I need to check about the header or pixel data of the 8-bit BMP files themselves? Or am I just missing a small change in my code that could make this work? It’s so frustrating because I’d really like to keep using `D3DXCreateTextureFromFileInMemoryEx` for its ease.

Any advice on this would be super helpful! I’m kind of at a standstill and would love to hear how others might have tackled similar issues. Thanks!

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    2 Answers

    1. The issue you’re experiencing with 8-bit BMP images is likely related to the format specifier you’re currently using. By passing D3DFMT_UNKNOWN, you rely on DirectX to automatically determine the correct format, but for palletized 8-bit BMP files, this detection can sometimes fail because they rely on a color palette rather than direct color values found in higher-bit-depth images. A safer approach might be explicitly specifying a compatible format such as D3DFMT_A8R8G8B8 or D3DFMT_X8R8G8B8. These formats request DirectX to convert or expand palette-indexed data into a known, supported RGB format during texture creation, often solving issues with loading 8-bit BMP files.

      If specifying a format explicitly doesn’t fully resolve the issue, ensure the image’s palette is properly defined and that no uncommon header values are present that might disrupt loading. It’s also helpful to check if the bitmap header follows the standard BITMAPINFOHEADER specification, as non-standard headers or compressed BMP formats may cause issues. Lastly, consider using a graphics or image-editing tool to resave the problematic BMP files into a known, simple format that DirectX easily accepts. This can help determine whether the issue lies in the BMP data format or elsewhere in your code. This combination of explicitly specifying a format and verifying image integrity typically addresses issues involving loading palette-based BMP images with DirectX 9.

    2. It sounds like you’re running into a classic issue with 8-bit BMP files. These files usually include a color palette that maps the pixel values to colors, which can be pretty tricky if your function isn’t set up to handle it.

      Since you’re using `D3DFMT_UNKNOWN`, DirectX doesn’t know how to handle the palette information for those 8-bit BMPs. You might want to specify the format more explicitly. For 8-bit BMP images, you can consider using `D3DFMT_PALETTE8` as the format. This could help DirectX interpret the pixel data correctly.

      Another thing to check is the BMP header and see if the color palette is present and properly formatted. If the palette is missing or corrupted, it can cause issues when rendering. Make sure your image loading routine correctly reads the palette entries and that the pixel data refers to those entries.

      You could also try to load these BMP files in a separate, simpler way first to ensure they’re valid. After confirming that, integrate back into your `LoadTexture` function. Also, look for any sources or libraries that specifically deal with BMP to understand how they handle color mappings.

      If nothing seems to work, you may need to transform the 8-bit BMP into a more manageable format before passing it to DirectX. Converting the image to a 24-bit format might be more straightforward for your current setup.

      Good luck! Debugging image loading can be a pain, but with a bit of tweaking, you’ll get it working.