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Implement subpixel font positioning

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Subpixel positioning is only by 1/3 of pixel
This commit is contained in:
Francesco Abbate
2021-03-03 18:36:09 +01:00
parent 8883685eea
commit 294f3f14fb
3 changed files with 22 additions and 12 deletions
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lib/font_renderer/font_renderer.cpp
+12 -3
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@@ -61,6 +61,10 @@ void FR_Renderer_Free(FR_Renderer *font_renderer) {
delete font_renderer;
}
int FR_Subpixel_Scale(FR_Renderer *font_renderer) {
return font_renderer->subpixel_scale();
}
int FR_Load_Font(FR_Renderer *font_renderer, const char *filename) {
bool success = font_renderer->renderer_alpha().load_font(filename);
return (success ? 0 : 1);
@@ -283,7 +287,9 @@ FR_Bitmap *FR_Bake_Font_Bitmap(FR_Renderer *font_renderer, int font_height,
glyph_info.xoff = 0;
glyph_info.yoff = -pad_y - gbounds.y2 + ascender_px;
glyph_info.xadvance = (x_next - x) / subpixel_scale;
// Note that below the xadvance is in pixels times the subpixel_scale.
// This is meant for subpixel positioning.
glyph_info.xadvance = roundf(x_next - x);
if (subpixel_scale != 1 && glyph_info.x1 > glyph_info.x0) {
glyph_lut_convolution(ren_buf, lcd_lut, cover_swap_buffer, glyph_info);
@@ -346,15 +352,18 @@ void blend_solid_hspan_subpixel(agg::rendering_buffer& rbuf, agg::lcd_distributi
// destination implicitly BGRA32. Source implictly single-byte renderer_alpha coverage with subpixel scale = 3.
// FIXME: consider using something like RenColor* instead of uint8_t * for dst.
void FR_Blend_Glyph(FR_Renderer *font_renderer, FR_Clip_Area *clip, int x, int y, uint8_t *dst, int dst_width, const FR_Bitmap *glyphs_bitmap, const FR_Bitmap_Glyph_Metrics *glyph, FR_Color color) {
void FR_Blend_Glyph(FR_Renderer *font_renderer, FR_Clip_Area *clip, int x_mult, int y, uint8_t *dst, int dst_width, const FR_Bitmap *glyphs_bitmap, const FR_Bitmap_Glyph_Metrics *glyph, FR_Color color) {
agg::lcd_distribution_lut& lcd_lut = font_renderer->lcd_distribution_lut();
const int subpixel_scale = font_renderer->subpixel_scale();
const int pixel_size = 4; // Pixel size for BGRA32 format.
int x = x_mult / subpixel_scale;
x += glyph->xoff;
y += glyph->yoff;
int glyph_x = glyph->x0, glyph_y = glyph->y0;
int glyph_x_subpixel = -(x_mult % subpixel_scale);
int glyph_width = glyph->x1 - glyph->x0;
int glyph_height = glyph->y1 - glyph->y0;
@@ -371,7 +380,7 @@ void FR_Blend_Glyph(FR_Renderer *font_renderer, FR_Clip_Area *clip, int x, int y
dst += (x + y * dst_width) * pixel_size;
agg::rendering_buffer dst_ren_buf(dst, glyph_width, glyph_height, dst_width * pixel_size);
uint8_t *src = glyphs_bitmap->pixels + (glyph_x + glyph_y * glyphs_bitmap->width) * subpixel_scale;
uint8_t *src = glyphs_bitmap->pixels + (glyph_x + glyph_y * glyphs_bitmap->width) * subpixel_scale + glyph_x_subpixel;
int src_stride = glyphs_bitmap->width * subpixel_scale;
const agg::rgba8 color_a(color.r, color.g, color.b);