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Support alpha blending.

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This commit is contained in:
Bram Stolk 2018-04-20 11:46:00 -07:00
parent 42dfaf3fff
commit 49e3970474
1 changed files with 26 additions and 2 deletions
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28
imcat.c
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@ -16,6 +16,8 @@
static int termw=0, termh=0;
static int doubleres=0;
static int blend=0;
static unsigned char termbg[3] = { 0,0,0 };
#if defined(_WIN64)
# include <windows.h>
@ -97,6 +99,15 @@ static void print_image_single_res( int w, int h, unsigned char* data )
# define HALFBLOCK "▀" // Uses Unicode char U+2580
#endif
#define BLEND \
{ \
const int t0 = a; \
const int t1 = 255-a; \
r = ( r * t0 + termbg[0] * t1 ) / 255; \
g = ( g * t0 + termbg[1] * t1 ) / 255; \
b = ( b * t0 + termbg[2] * t1 ) / 255; \
}
static void print_image_double_res( int w, int h, unsigned char* data )
{
if ( h & 1 )
@ -119,7 +130,8 @@ static void print_image_double_res( int w, int h, unsigned char* data )
unsigned char g = *row0++;
unsigned char b = *row0++;
unsigned char a = *row0++;
(void) a;
if ( blend )
BLEND
snprintf( tripl, sizeof(tripl), "%d;%d;%dm", r,g,b );
strncat( line, tripl, sizeof(line) - strlen(line) - 1 );
// background colour.
@ -128,7 +140,8 @@ static void print_image_double_res( int w, int h, unsigned char* data )
g = *row1++;
b = *row1++;
a = *row1++;
(void) a;
if ( blend )
BLEND
snprintf( tripl, sizeof(tripl), "%d;%d;%dm" HALFBLOCK, r,g,b );
strncat( line, tripl, sizeof(line) - strlen(line) - 1 );
}
@ -210,6 +223,17 @@ int main( int argc, char* argv[] )
exit( 0 );
}
// Parse environment variable for terminal background colour.
const char* imcatbg = getenv( "IMCATBG" );
if ( imcatbg )
{
const int bg = strtol( imcatbg+1, 0, 16 );
termbg[ 2 ] = ( bg >> 0 ) & 0xff;
termbg[ 1 ] = ( bg >> 8 ) & 0xff;
termbg[ 0 ] = ( bg >> 16 ) & 0xff;
blend = 1;
}
// Step 0: Windows cmd.exe needs to be put in proper console mode.
set_console_mode();