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Fix alpha blitting once and for all

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This commit is contained in:
Kevin Lange 2013-03-29 00:34:12 -07:00
parent 2d7a29d17e
commit 8e48ee8cfa
4 changed files with 49 additions and 18 deletions
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7
userspace/gui/terminal/terminal.c
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@ -725,6 +725,7 @@ FT_Face face_extra;
FT_GlyphSlot slot;
FT_UInt glyph_index;
void drawChar(FT_Bitmap * bitmap, int x, int y, uint32_t fg, uint32_t bg) {
int i, j, p, q;
int x_max = x + bitmap->width;
@ -732,7 +733,7 @@ void drawChar(FT_Bitmap * bitmap, int x, int y, uint32_t fg, uint32_t bg) {
for (j = y, q = 0; j < y_max; j++, q++) {
for ( i = x, p = 0; i < x_max; i++, p++) {
uint32_t tmp = (fg & 0xFFFFFF) | 0x1000000 * bitmap->buffer[q * bitmap->width + p];
term_set_point(i,j, alpha_blend_rgba(bg, tmp));
term_set_point(i,j, alpha_blend_rgba(premultiply(bg), premultiply(tmp)));
}
}
}
@ -802,13 +803,13 @@ term_write_char(
if (val == 0xFFFF) { return; } /* Unicode, do not redraw here */
for (uint8_t i = 0; i < char_height; ++i) {
for (uint8_t j = 0; j < char_width; ++j) {
term_set_point(x+j,y+i,_bg);
term_set_point(x+j,y+i,premultiply(_bg));
}
}
if (flags & ANSI_WIDE) {
for (uint8_t i = 0; i < char_height; ++i) {
for (uint8_t j = char_width; j < 2 * char_width; ++j) {
term_set_point(x+j,y+i,_bg);
term_set_point(x+j,y+i,premultiply(_bg));
}
}
}

55
userspace/lib/graphics.c
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@ -12,6 +12,23 @@
#define PNG_DEBUG 3
#include <png.h>
static inline int32_t min(int32_t a, int32_t b) {
return (a < b) ? a : b;
}
static inline int32_t max(int32_t a, int32_t b) {
return (a > b) ? a : b;
}
static inline uint16_t min16(uint16_t a, uint16_t b) {
return (a < b) ? a : b;
}
static inline uint16_t max16(uint16_t a, uint16_t b) {
return (a > b) ? a : b;
}
/* Pointer to graphics memory */
void flip(gfx_context_t * ctx) {
@ -131,16 +148,34 @@ uint32_t alpha_blend(uint32_t bottom, uint32_t top, uint32_t mask) {
return rgba(red,gre,blu, alp);
}
#define DONT_USE_FLOAT_FOR_ALPHA 1
uint32_t alpha_blend_rgba(uint32_t bottom, uint32_t top) {
uint8_t a = _ALP(top);
uint8_t b = ((int)_ALP(bottom) * (255 - a)) / 255;
uint8_t alp = a + b;
uint8_t red = alp ? (int)(_RED(bottom) * (b) + _RED(top) * a) / (alp): 0;
uint8_t gre = alp ? (int)(_GRE(bottom) * (b) + _GRE(top) * a) / (alp): 0;
uint8_t blu = alp ? (int)(_BLU(bottom) * (b) + _BLU(top) * a) / (alp): 0;
if (_ALP(bottom) == 0) return top;
if (_ALP(top) == 255) return top;
if (_ALP(top) == 0) return bottom;
#if DONT_USE_FLOAT_FOR_ALPHA
uint16_t a = _ALP(top);
uint16_t c = 255 - a;
uint16_t b = ((int)_ALP(bottom) * c) / 255;
uint16_t alp = min16(a + b, 255);
uint16_t red = min16((uint32_t)(_RED(bottom) * c + _RED(top) * 255) / 255, 255);
uint16_t gre = min16((uint32_t)(_GRE(bottom) * c + _GRE(top) * 255) / 255, 255);
uint16_t blu = min16((uint32_t)(_BLU(bottom) * c + _BLU(top) * 255) / 255, 255);
return rgba(red,gre,blu,alp);
#else
double a = _ALP(top) / 255.0;
double c = 1.0 - a;
double b = (_ALP(bottom) / 255.0) * c;
double alp = a + b; if (alp > 1.0) alp = 1.0;
double red = (_RED(bottom) / 255.0) * c + (_RED(top) / 255.0); if (red > 1.0) red = 1.0;
double gre = (_GRE(bottom) / 255.0) * c + (_GRE(top) / 255.0); if (gre > 1.0) gre = 1.0;
double blu = (_BLU(bottom) / 255.0) * c + (_BLU(top) / 255.0); if (blu > 1.0) blu = 1.0;
return rgba(red * 255, gre * 255, blu * 255, alp * 255);
#endif
}
uint32_t premultiply(uint32_t color) {
uint16_t a = _ALP(color);
uint16_t r = _RED(color);
@ -408,14 +443,6 @@ void context_to_png(FILE * file, gfx_context_t * ctx) {
}
static inline int32_t min(int32_t a, int32_t b) {
return (a < b) ? a : b;
}
static inline int32_t max(int32_t a, int32_t b) {
return (a > b) ? a : b;
}
void draw_sprite(gfx_context_t * ctx, sprite_t * sprite, int32_t x, int32_t y) {
int32_t _left = max(x, 0);
int32_t _top = max(y, 0);

3
userspace/lib/graphics.h
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@ -76,4 +76,7 @@ void draw_sprite_scaled(gfx_context_t * ctx, sprite_t * sprite, int32_t x, int32
void context_to_png(FILE * file, gfx_context_t * ctx);
uint32_t premultiply(uint32_t color);
#endif

2
userspace/tests/test-echo.c
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@ -14,7 +14,7 @@ int main(int argc, char ** argv) {
printf("\033[38;2;178;213;238mHello World\033[0m\n");
for (int i = 0; i < 256; i += 3) {
printf("\033[48;6;30;30;30;%dmX\033[0m", i);
printf("\033[48;6;255;0;0;%dmX\033[0m", i);
}
printf("\n");