嘗試將FreeType與CImg一起使用

Question

我使用一些使用FreeType2的代碼：

void drawText( FT_Face &face, cimg_library::CImg < unsigned char > &image, const int &heightText, const std::wstring &text, const int &leftTopX, const int &leftTopY, int &width, int &height, unsigned char fontColor[] = NULL, const int separeteGlyphWidth = 1 ) {

    width = 0;
    height = 0;

    FT_Set_Pixel_Sizes( face, 0, heightText );
    FT_GlyphSlot glyphSlot = face->glyph;  

    int shiftX = leftTopX;
    int shiftY = 0;
    for( int numberSymbol = 0; numberSymbol < text.length(); ++numberSymbol ){

        shiftY = leftTopY;

        bool isSpace = false;
        FT_ULong symbol = text[ numberSymbol ]; //FT_ULong symbol = text.at(numberSymbol);
        if (symbol == ' ') {
            symbol = 'a';
            isSpace = true;
        }

        if( FT_Load_Char( face, symbol, FT_LOAD_RENDER ) ) throw "Error, glyph not load!! \n";

        shiftY = heightText - glyphSlot->bitmap.rows;
        if ( shiftY < 0 ) shiftY = 0;

        std::cout << "char: " << (char) text.at( numberSymbol ) << " \tshiftY = " << shiftY << "\t rows = " << glyphSlot->bitmap.rows << "\t extra = " << ( glyphSlot->advance.y >> 6 ) << "\n";

        if ( !isSpace ) drawGlyph( glyphSlot, image, shiftX, shiftY, fontColor );

        shiftX += glyphSlot->bitmap.width + separeteGlyphWidth;

        if( height < shiftY + glyphSlot->bitmap.rows ) height = shiftY + glyphSlot->bitmap.rows;
        width = shiftX;

    }

}


std::string str = "Let me speak from my heart!";
std::wstring wStr( str.begin(), str.end() );

int width, height;
drawText( face, myCImg, 50, wStr, 50, 50, width, height );

但效果不理想。 輸出圖像如下所示：

帶有符號的行為有些奇怪：“ y”，“ f”，“ p”。 如何降低它？

看來我應該使用glyphSlot-> metrics.vertAdvance做些什么，但我不知道如何正確使用它。

Answer 1

快速瀏覽在線參考 ，如果需要像素坐標，則似乎用於Y偏移的值應基於bitmap_top 。

所以我建議換線

shiftY = heightText - glyphSlot->bitmap.rows;

至

shiftY = heightText - glyphSlot->bitmap_top;

通過看一下以下列方式使用這些值的基礎教程 ，似乎也可以肯定這一點：

/* now, draw to our target surface */
my_draw_bitmap( &slot->bitmap,
              pen_x + slot->bitmap_left,
              pen_y - slot->bitmap_top );

/* increment pen position */
pen_x += slot->advance.x >> 6;