// 範例程式: 讀取  GIF 影像中的調色盤資料
// 2009/12/17  by Yeuan-Kuen Lee
// yeuankuenlee@gmail.com

// 全域變數宣告

typedef struct {
    Byte bBlue;
    Byte bGreen;
    Byte bRed;
    } COLOR_TYPE;

COLOR_TYPE crColor[1];
COLOR_TYPE crPalette[256];
COLOR_TYPE crSortedPalette[256];
float fLuminance[256];


void __fastcall TForm1::ReadGIFPalette1Click(TObject *Sender)
{
    FILE *imGIF;
    BYTE bM, bCR, bPixel;
    int iCornerX,iCornerY;

    pcImageMode->ActivePage = tsPalette;
    OpenDialog1->FilterIndex = 2;
    OpenDialog1->Execute();
    lblGIFFileName->Caption = "File Name: "+OpenDialog1->FileName;

    imPalette->Canvas->Brush->Color = clWhite;
    imPalette->Canvas->FillRect(Rect(0,0,323,323));

    for (i=0;i<256;i++)
        {
        crPalette[i].bRed=0;
        crPalette[i].bGreen=0;
        crPalette[i].bBlue=0;
        crSortedPalette[i].bRed = 0;
        crSortedPalette[i].bGreen = 0;
        crSortedPalette[i].bBlue = 0;
        fLuminance[i]=0;
        }

    imGIF = fopen(OpenDialog1->FileName.c_str(), "rb");
    // Read Header..
    fseek(imGIF,0L,SEEK_SET);
    fread(GIFHeader,13,1,imGIF);
    lblVersion->Caption = "Version: " + AnsiString(GIFHeader[0].cVersion[0])+AnsiString(GIFHeader[0].cVersion[1])+AnsiString(GIFHeader[0].cVersion[2])+AnsiString(GIFHeader[0].cVersion[3])+AnsiString(GIFHeader[0].cVersion[4])+AnsiString(GIFHeader[0].cVersion[5]);
    iImageWidth = GIFHeader[0].bScreenWidth[0]+ GIFHeader[0].bScreenWidth[1] * 256;
    iImageHeight = GIFHeader[0].bScreenHeight[0]+ GIFHeader[0].bScreenHeight[1] * 256;
    lblScreenWidth->Caption = "Screen Width : " + AnsiString(iImageWidth);
    lblScreenHeight->Caption = "Screen Height : " + AnsiString(iImageHeight);

    bM = GIFHeader[0].bMCrPixel >> 7;
    lblM->Caption = "M: " + AnsiString(bM);
    bCR = GIFHeader[0].bMCrPixel << 1;
    bCR = bCR >> 5;
    bCR = bCR + 1;
    lblCR->Caption = "CR: " + AnsiString(bCR);

    bPixel = GIFHeader[0].bMCrPixel << 5;
    bPixel = bPixel >> 5;
    bPixel = bPixel + 1;
    lblPixel->Caption = "Pixel: " + AnsiString(bPixel);
    lblBackgroundColor->Caption= "Background Color Index: "+AnsiString(GIFHeader[0].bBackgroundColorIndex);

    iTotalColor = 1;
    for (i=0;i<bPixel;i++)
       iTotalColor = iTotalColor * 2;
    lblTotalColor->Caption = "Total Color: "+AnsiString(iTotalColor);
    iRowCount = iTotalColor / 16;
    if ((iTotalColor % 16)!= 0)
        iRowCount++; 

    // 開始讀取調色盤資料
    if ( bM == 1)
        {
        fread(crPalette,3,iTotalColor,imGIF);
        for (i=0;i<iRowCount;i++)
            for (j=0;j<16;j++)
                {
                k = i * 16 + j;
                if (k < iTotalColor)
                    {
                    imPalette->Canvas->Brush->Color =(TColor)RGB(crPalette[k].bRed,crPalette[k].bGreen,crPalette[k].bBlue);
                    fLuminance[k] = 0.299*crPalette[k].bRed + 0.587*crPalette[k].bGreen + 0.114 * crPalette[k].bBlue;
                    crSortedPalette[k].bRed = crPalette[k].bRed;
                    crSortedPalette[k].bGreen = crPalette[k].bGreen;
                    crSortedPalette[k].bBlue = crPalette[k].bBlue;
                    iCornerX = i * 20 + 4;
                    iCornerY = j * 20 + 4;
                    imPalette->Canvas->FillRect(Rect(iCornerY,iCornerX,iCornerY+16,iCornerX+16));
                    }
                }
        }


}