diff --git a/qoi.h b/qoi.h index 0aec728..a16262f 100644 --- a/qoi.h +++ b/qoi.h @@ -122,24 +122,14 @@ The possible chunks are: 6-bit index into the color index array: 0..63 - - QOI_RUN_8 ------------- + - QOI_RUN --------------- | Byte[0] | | 7 6 5 4 3 2 1 0 | -|----------+--------------| -| 0 1 0 | run | +|-------+-----------------| +| 0 1 | run | -3-bit tag b010 -5-bit run-length repeating the previous pixel: 1..32 - - - - QOI_RUN_16 -------------------------------------- -| Byte[0] | Byte[1] | -| 7 6 5 4 3 2 1 0 | 7 6 5 4 3 2 1 0 | -|----------+----------------------------------------| -| 0 1 1 | run | - -3-bit tag b011 -13-bit run-length repeating the previous pixel: 33..8224 +2-bit tag b01 +6-bit run-length repeating the previous pixel: 1..64 - QOI_DIFF_8 ------------ @@ -160,14 +150,33 @@ so "1 - 2" will result in 255, while "255 + 1" will result in 0. - QOI_DIFF_16 ------------------------------------- | Byte[0] | Byte[1] | | 7 6 5 4 3 2 1 0 | 7 6 5 4 3 2 1 0 | -|----------+--------------|------------ +-----------| -| 1 1 0 | red diff | green diff | blue diff | +|-------------+-----------|------------ +-----------| +| 1 1 0 0 | red diff | green diff | blue diff | -3-bit tag b110 -5-bit red channel difference from the previous pixel between -16..15 +4-bit tag b1100 +4-bit red channel difference from the previous pixel between -8..7 4-bit green channel difference from the previous pixel between -8..7 4-bit blue channel difference from the previous pixel between -8..7 +The difference to the current channel values are using a wraparound operation, +so "5 - 8" will result in 253, while "250 + 7" will result in 1. + + + - QOI_GDIFF_16 ------------------------------------ +| Byte[0] | Byte[1] | +| 7 6 5 4 3 2 1 0 | 7 6 5 4 3 2 1 0 | +|-------------+--------+-------------------+--------| +| 1 1 0 1 | dr-dg | green diff | db-dg | + +4-bit tag b1101 +3-bit red channel difference minus green channel difference -4..3 +6-bit green channel difference from the previous pixel -32..31 +3-bit blue channel difference minus green channel difference -4..3 + +The green channel is used to indicate the general direction of change and gets +a few more bits. dr and db base their diffs off of the green channel diff. E.g. + dr = (last_px.r - cur_px.r) - (last_px.g - cur_px.g) + The difference to the current channel values are using a wraparound operation, so "10 - 13" will result in 253, while "250 + 7" will result in 1. @@ -309,17 +318,16 @@ void *qoi_decode(const void *data, int size, qoi_desc *desc, int channels); #define QOI_FREE(p) free(p) #endif -#define QOI_INDEX 0x00 // 00xxxxxx -#define QOI_RUN_8 0x40 // 010xxxxx -#define QOI_RUN_16 0x60 // 011xxxxx -#define QOI_DIFF_8 0x80 // 10xxxxxx -#define QOI_DIFF_16 0xc0 // 110xxxxx -#define QOI_DIFF_24 0xe0 // 1110xxxx -#define QOI_COLOR 0xf0 // 1111xxxx +#define QOI_INDEX 0x00 // 00xxxxxx +#define QOI_RUN 0x40 // 01xxxxxx +#define QOI_DIFF_8 0x80 // 10xxxxxx +#define QOI_DIFF_16 0xc0 // 1100xxxx +#define QOI_GDIFF_16 0xd0 // 1101xxxx +#define QOI_DIFF_24 0xe0 // 1110xxxx +#define QOI_COLOR 0xf0 // 1111xxxx -#define QOI_MASK_2 0xc0 // 11000000 -#define QOI_MASK_3 0xe0 // 11100000 -#define QOI_MASK_4 0xf0 // 11110000 +#define QOI_MASK_2 0xc0 // 11000000 +#define QOI_MASK_4 0xf0 // 11110000 #define QOI_COLOR_HASH(C) (C.rgba.r ^ C.rgba.g ^ C.rgba.b ^ C.rgba.a) #define QOI_MAGIC \ @@ -403,17 +411,9 @@ void *qoi_encode(const void *data, const qoi_desc *desc, int *out_len) { if ( run > 0 && - (run == 0x2020 || px.v != px_prev.v || px_pos == px_end) + (run == 64 || px.v != px_prev.v || px_pos == px_end) ) { - if (run < 33) { - run -= 1; - bytes[p++] = QOI_RUN_8 | run; - } - else { - run -= 33; - bytes[p++] = QOI_RUN_16 | run >> 8; - bytes[p++] = run; - } + bytes[p++] = QOI_RUN | (run - 1); run = 0; } @@ -426,39 +426,49 @@ void *qoi_encode(const void *data, const qoi_desc *desc, int *out_len) { else { index[index_pos] = px; - int vr = px.rgba.r - px_prev.rgba.r; - int vg = px.rgba.g - px_prev.rgba.g; - int vb = px.rgba.b - px_prev.rgba.b; - int va = px.rgba.a - px_prev.rgba.a; - + char vr = px.rgba.r - px_prev.rgba.r; + char vg = px.rgba.g - px_prev.rgba.g; + char vb = px.rgba.b - px_prev.rgba.b; + char va = px.rgba.a - px_prev.rgba.a; + + char vg_r = vr - vg; + char vg_b = vb - vg; + if ( + va == 0 && + vr > -3 && vr < 2 && + vg > -3 && vg < 2 && + vb > -3 && vb < 2 + ) { + bytes[p++] = QOI_DIFF_8 | ((vr + 2) << 4) | (vg + 2) << 2 | (vb + 2); + } + else if ( + va == 0 && + vr > -9 && vr < 8 && + vg > -9 && vg < 8 && + vb > -9 && vb < 8 + ) { + bytes[p++] = QOI_DIFF_16 | (vr + 8); + bytes[p++] = (vg + 8) << 4 | (vb + 8); + } + else if ( + va == 0 && + vg_r > -5 && vg_r < 4 && + vg > -33 && vg < 32 && + vg_b > -5 && vg_b < 4 + ) { + bytes[p++] = QOI_GDIFF_16 | (vg_r + 4) << 1 | (vg + 32) >> 5; + bytes[p++] = (vg + 32) << 3 | (vg_b + 4); + } + else if ( vr > -17 && vr < 16 && vg > -17 && vg < 16 && vb > -17 && vb < 16 && va > -17 && va < 16 ) { - if ( - va == 0 && - vr > -3 && vr < 2 && - vg > -3 && vg < 2 && - vb > -3 && vb < 2 - ) { - bytes[p++] = QOI_DIFF_8 | ((vr + 2) << 4) | (vg + 2) << 2 | (vb + 2); - } - else if ( - va == 0 && - vr > -17 && vr < 16 && - vg > -9 && vg < 8 && - vb > -9 && vb < 8 - ) { - bytes[p++] = QOI_DIFF_16 | (vr + 16); - bytes[p++] = (vg + 8) << 4 | (vb + 8); - } - else { - bytes[p++] = QOI_DIFF_24 | (vr + 16) >> 1; - bytes[p++] = (vr + 16) << 7 | (vg + 16) << 2 | (vb + 16) >> 3; - bytes[p++] = (vb + 16) << 5 | (va + 16); - } + bytes[p++] = QOI_DIFF_24 | (vr + 16) >> 1; + bytes[p++] = (vr + 16) << 7 | (vg + 16) << 2 | (vb + 16) >> 3; + bytes[p++] = (vb + 16) << 5 | (va + 16); } else { bytes[p++] = QOI_COLOR | (vr ? 8 : 0) | (vg ? 4 : 0) | (vb ? 2 : 0) | (va ? 1 : 0); @@ -531,23 +541,26 @@ void *qoi_decode(const void *data, int size, qoi_desc *desc, int channels) { if ((b1 & QOI_MASK_2) == QOI_INDEX) { px = index[b1 ^ QOI_INDEX]; } - else if ((b1 & QOI_MASK_3) == QOI_RUN_8) { - run = (b1 & 0x1f); - } - else if ((b1 & QOI_MASK_3) == QOI_RUN_16) { - int b2 = bytes[p++]; - run = (((b1 & 0x1f) << 8) | (b2)) + 32; + else if ((b1 & QOI_MASK_2) == QOI_RUN) { + run = (b1 & 0x3f); } else if ((b1 & QOI_MASK_2) == QOI_DIFF_8) { px.rgba.r += ((b1 >> 4) & 0x03) - 2; px.rgba.g += ((b1 >> 2) & 0x03) - 2; px.rgba.b += ( b1 & 0x03) - 2; } - else if ((b1 & QOI_MASK_3) == QOI_DIFF_16) { + else if ((b1 & QOI_MASK_4) == QOI_DIFF_16) { int b2 = bytes[p++]; - px.rgba.r += (b1 & 0x1f) - 16; - px.rgba.g += (b2 >> 4) - 8; - px.rgba.b += (b2 & 0x0f) - 8; + px.rgba.r += (b1 & 0x0f) - 8; + px.rgba.g += (b2 >> 4) - 8; + px.rgba.b += (b2 & 0x0f) - 8; + } + else if ((b1 & QOI_MASK_4) == QOI_GDIFF_16) { + int b2 = bytes[p++]; + int vg = ((b1 & 0x01) << 5 | (b2 & 0xf8) >> 3) - 32; + px.rgba.r += vg - 4 + ((b1 & 0x0e) >> 1); + px.rgba.g += vg; + px.rgba.b += vg - 4 + (b2 & 0x07); } else if ((b1 & QOI_MASK_4) == QOI_DIFF_24) { int b2 = bytes[p++];