我正在通過 GDI 函式 LoadImage 從檔案（BMP 型別）加載位圖影像，該函式回傳位圖句柄。
我知道如何訪問位圖位。但影像采用 8BPP 格式，因此調色。如何獲取調色板條目？
uj5u.com熱心網友回復：
選擇 dc 中的位圖并呼叫GetDIBColorTable. 可以在此處使用臨時記憶體 dc：
RGBQUAD rgb[256] = { 0 };
HDC memdc = CreateCompatibleDC(hdc);
auto oldbmp = SelectObject(memdc, hbitmap);
GetDIBColorTable(memdc, 0, 256, rgb);
SelectObject(memdc, oldbmp);
DeleteDC(memdc);
或者用于GetDIBits閱讀BITMAPINFO。您必須保留足夠的記憶體來讀取顏色表 所有位元組 sizeof(BITMAPINFO)。
顏色表將被復制到BITMAPINFO->bmiColors
Gdi 是另一種選擇。這是 GDI 示例：
int main()
{
HBITMAP hbitmap = (HBITMAP)LoadImage(0, L"source.bmp",
IMAGE_BITMAP, 0, 0, LR_CREATEDIBSECTION | LR_DEFAULTSIZE | LR_LOADFROMFILE);
if (!hbitmap)
return 0;
BITMAP bm;
GetObject(hbitmap, sizeof(bm), &bm);
int width = bm.bmWidth;
int height = bm.bmHeight;
WORD clrbits = (WORD)(bm.bmPlanes * bm.bmBitsPixel);
if (clrbits == 8) clrbits = 1;
else if (clrbits <= 4) clrbits = 4;
else if (clrbits <= 8) clrbits = 8;
else if (clrbits <= 16) clrbits = 16;
else if (clrbits <= 24) clrbits = 24;
else clrbits = 32;
HDC hdc = GetDC(0);
if(clrbits == 8)
{
RGBQUAD rgb[256] = { 0 };
HDC memdc = CreateCompatibleDC(hdc);
auto oldbmp = SelectObject(memdc, hbitmap);
GetDIBColorTable(memdc, 0, 256, rgb);
SelectObject(memdc, oldbmp);
DeleteDC(memdc);
}
int palette_size = (clrbits < 24) ? sizeof(RGBQUAD) * (1 << clrbits) : 0;
BITMAPINFO* bmpinfo = (BITMAPINFO*)new BYTE[sizeof(BITMAPINFO) palette_size];
int width_in_bytes = ((width * clrbits 31) & ~31) / 8;
DWORD size = width_in_bytes * height;
bmpinfo->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmpinfo->bmiHeader.biWidth = width;
bmpinfo->bmiHeader.biHeight = height;
bmpinfo->bmiHeader.biPlanes = bm.bmPlanes;
bmpinfo->bmiHeader.biBitCount = bm.bmBitsPixel;
bmpinfo->bmiHeader.biClrUsed = (clrbits < 24) ? (1 << clrbits) : 0;
bmpinfo->bmiHeader.biCompression = BI_RGB;
bmpinfo->bmiHeader.biSizeImage = size;
BYTE* bits = new BYTE[size];
GetDIBits(hdc, hbitmap, 0, height, bits, bmpinfo, 0);
//palette size should be 1024 for 256 color
//it should be stored in `bmpinfo->bmiColors`
delete[]bits;
delete[](BYTE*)bmpinfo;
DeleteObject(hbitmap);
ReleaseDC(0, hdc);
return 0;
}
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