[ft] How to generate a glyph bitmap of a specific pixel size using FT_Set_Pixel_Sizes

[Z C]

I called FT_Set_Pixel_Sizes(face, 40, 20); hoping to get a glyph of 20x40 dimension in pixels, but when I used face->glyph->bitmap to access the bitmap, its dimension is 26*14

Below is my code:

FT_Library library;

if (FT_Init_FreeType(&library) != FT_Err_Ok) throw runtime_error("Failed to load freetype library");

FT_Face face;

if (FT_New_Memory_Face(library, fontData, fontDataSize, faceIndex, &face) != FT_Err_Ok) throw runtime_error("Failed to load face from font file");

FT_Set_Pixel_Sizes(face, 40, 20);

int glyphIndex = FT_Get_Char_Index(face, 65); // 65 is 'A'

if (glyphIndex == 0) throw runtime_error("Character doesn't exist in font");

FT_Load_Glyph(face, glyphIndex, FT_LOAD_DEFAULT);

if (face->glyph->format != FT_GLYPH_FORMAT_BITMAP)

FT_Render_Glyph(face->glyph, FT_RENDER_MODE_NORMAL);

FT_Bitmap bitmap = face->glyph->bitmap;

cout<<bitmap.rows<<' '<<bitmap.width<<endl;