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kitty_null: only null out alphas, not RGB #1440

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nick black 2021-04-26 00:19:34 -04:00 committed by Nick Black
parent b075ecd383
commit a19b945ec6
1 changed files with 35 additions and 20 deletions
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55
src/lib/kitty.c
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@ -113,7 +113,25 @@ base64_rgba3(const uint32_t* pixels, size_t pcount, char* b64, bool wipe[static
// 16 bytes when base64 encoded). skip the initial |skip| pixels, and null out a maximum
// of |max| pixels after that. returns the number of pixels nulled out. |max| must be
// positive. |skip| must be non-negative, and less than 3. |pleft| is the number of pixels
// available in the chunk.
// available in the chunk. the RGB is 24 bits, and thus 4 base64 bytes, but
// unfortunately don't always start on a byte boundary =[.
// 0: R1(0..5)
// 1: R1(6..7), G1(0..3)
// 2: G1(4..7), B1(0..1)
// 3: B1(2..7)
// 4: A1(0..5)
// 5: A1(6..7), R2(0..3)
// 6: R2(4..7), G2(0..1)
// 7: G2(2..7)
// 8: B2(0..5)
// 9: B2(6..7), A2(0..3)
// A: A2(4..7), R3(0..1)
// B: R3(2..7)
// C: G3(0..5)
// D: G3(6..7), B3(0..3)
// E: B3(4..7), A3(0..1)
// F: A3(2..7)
// so we will only ever zero out bytes 4, 5, 9, A, E, and F
static inline int
kitty_null(char* triplet, int skip, int max, int pleft){
//fprintf(stderr, "SKIP/MAX/PLEFT %d/%d/%d\n", skip, max, pleft);
@ -125,29 +143,26 @@ kitty_null(char* triplet, int skip, int max, int pleft){
}
//fprintf(stderr, "alpha-nulling %d after %d\n", max, skip);
if(skip == 0){
if(max == 1){
memset(triplet, b64subs[0], 5);
triplet[5] = b64subs[b64idx(triplet[5]) & 0xf];
}else if(max == 2){
memset(triplet, b64subs[0], 10);
triplet[10] = b64subs[b64idx(triplet[10]) & 0x3];
}else{ // max == 3
memset(triplet, b64subs[0], 16);
triplet[0x4] = b64subs[0];
triplet[0x5] = b64subs[b64idx(triplet[0x5]) & 0xf];
if(max > 1){
triplet[0x9] = b64subs[b64idx(triplet[0x9]) & 0x30];
triplet[0xA] = b64subs[b64idx(triplet[0xA]) & 0x3];
}
if(max == 3){
triplet[0xE] = b64subs[b64idx(triplet[0xE]) & 0x3c];
triplet[0xF] = b64subs[0];
}
}else if(skip == 1){
if(max == 1){
triplet[5] = b64subs[b64idx(triplet[5]) & 0x30];
memset(triplet + 6, b64subs[0], 4);
triplet[10] = b64subs[b64idx(triplet[10]) & 0x3];
}else{
triplet[5] = b64subs[b64idx(triplet[5]) & 0x30];
memset(triplet + 6, b64subs[0], 10);
triplet[0x9] = b64subs[b64idx(triplet[0x9]) & 0x30];
triplet[0xA] = b64subs[b64idx(triplet[0xA]) & 0x3];
if(max == 2){
triplet[0xE] = b64subs[b64idx(triplet[0xE]) & 0x3c];
triplet[0xF] = b64subs[0];
}
}else{ // skip == 2
if(max == 1){
triplet[10] = b64subs[b64idx(triplet[10]) & 0xf];
memset(triplet + 11, b64subs[0], 5);
}
triplet[0xE] = b64subs[b64idx(triplet[0xE]) & 0x3c];
triplet[0xF] = b64subs[0];
}
return max;
}