Author: wmb Date: Mon Jan 17 22:58:06 2011 New Revision: 2111 URL: http://tracker.coreboot.org/trac/openfirmware/changeset/2111
Log: Initial revision of color space converstion code.
Added: dev/olpc/viacamera/ycrcbtorgb.fth
Added: dev/olpc/viacamera/ycrcbtorgb.fth ============================================================================== --- /dev/null 00:00:00 1970 (empty, because file is newly added) +++ dev/olpc/viacamera/ycrcbtorgb.fth Mon Jan 17 22:58:06 2011 (r2111) @@ -0,0 +1,141 @@ +\ See license at end of file +purpose: Color space conversion from YCbCr to RGB + +\ R = clip (Y + 1.402 * Cr) +\ G = clip (Y - 0.344 * Cb - 0.714 * Cr) +\ B = clip (Y + 1.772 * Cb) + +\ This is for full-range YCbCr, where the Y anc Cb/Cr values ranges from 0-255. +\ For restricted-range YCbCr (16 <= Y <= 235, 16 <= Cr,Cb <= 240), the Y value +\ would need to be adjusted to Ysc = (Y - 16) * 1.164 (1.164 = 298 / 256 = 149 / 128) +\ and the multipliers change from (1.402, -0.343, -0.711, 1.765) to (1.596, -0.392, -0.813, 2.017) + +code ycrcb444>rgb888 ( y cr cb -- r g b ) + \ y: 8 [sp] + \ u: 4 [sp] = Cr + \ v: 0 [sp] = Cb + + d# 128 # 0 [sp] sub \ convert Cb to signed + d# 128 # 4 [sp] sub \ convert Cr to signed + 8 [sp] bx mov \ Get Y into register + + d# 90 # 4 [sp] ax imul-imm \ Multiply Cr by 1.402 * 64 (actually 1.406) + d# 6 # ax sar \ Scale down by 64 + bx ax add \ Add to Y + 0< if ax ax xor then \ Clip to 0 + d# 255 # ax cmp > if d# 255 # ax mov then \ Clip to 255 + + ax 8 [sp] mov \ Put R in place on stack + + d# -46 # 4 [sp] ax imul-imm \ Multiply Cr by -0.714 * 64 (actually -0.719) + d# 6 # ax sar \ Scale down by 64 + ax cx mov + d# -22 # 0 [sp] ax imul-imm \ Multiply Cr by -0.344 * 64 (actually -0.344) + d# 6 # ax sar \ Scale down by 64 + ax cx add + bx cx add \ Now we have G + 0< if cx cx xor then \ Clip to 0 + d# 255 # cx cmp > if d# 255 # cx mov then \ Clip to 255 + + d# 113 # 0 [sp] ax imul-imm \ Multiply Cr by 1.772 * 64 (actually 1.766) + d# 6 # ax sar \ Scale down by 64 + bx ax add \ Add to Y + 0< if ax ax xor then \ Clip to 0 + d# 255 # ax cmp > if d# 255 # ax mov then \ Clip to 255 + ax 0 [sp] mov \ Put B in place on stack + + cx 4 [sp] mov \ Put G in place on stack +c; + + +\ This version operates on pixel values in memory +\ Src bytes are Cb Y1 Cr Y2 (2 pixels) +\ Dst bytes are R G B A R G B A (2 pixels) + +code ycbcr422>rgba8888 ( src dst count -- ) + 4 [sp] di xchg \ di: dst + 8 [sp] si xchg \ si: src + + ax push ax push \ Space on stack for Cr and Cb values + + begin + \ src: Cb Y1 Cr Y2 dst: R1 G1 B1 A1 R2 G2 B2 A2 + ax ax xor al lods d# 128 # ax sub ax 0 [sp] mov \ Get Cb, make signed, save on stack + ax ax xor al lods ax bx mov \ Get Y1, save in BX + ax ax xor al lods d# 128 # ax sub ax 4 [sp] mov \ Get Cr, make signed, save on stack + + d# 90 # 4 [sp] ax imul-imm \ Multiply Cr by 1.402 * 64 (actually 1.406) + d# 6 # ax sar \ Scale down by 64 + bx ax add \ Add to Y + + 0< if ax ax xor then \ Clip to 0 + d# 255 # ax cmp > if d# 255 # ax mov then \ Clip to 255 + + al stos \ Output R + + d# -46 # 4 [sp] ax imul-imm \ Multiply Cr by -0.714 * 64 (actually -0.719) + d# 6 # ax sar \ Scale down by 64 + ax dx mov + d# -22 # 0 [sp] ax imul-imm \ Multiply Cr by -0.344 * 64 (actually -0.344) + d# 6 # ax sar \ Scale down by 64 + dx ax add + bx ax add \ Now we have G + + 0< if ax ax xor then \ Clip to 0 + d# 255 # ax cmp > if d# 255 # ax mov then \ Clip to 255 + + al stos \ Output G + + d# 113 # 0 [sp] ax imul-imm \ Multiply Cr by 1.772 * 64 (actually 1.766) + d# 6 # ax sar \ Scale down by 64 + bx ax add \ Add to Y + + 0< if ax ax xor then \ Clip to 0 + d# 255 # ax cmp > if d# 255 # ax mov then \ Clip to 255 + + al stos \ Output B + d# 255 # al mov + al stos \ Output A + + ax ax xor al lods ax bx mov \ Get Y2 into BX + + d# 90 # 4 [sp] ax imul-imm \ Multiply Cr by 1.402 * 64 (actually 1.406) + d# 6 # ax sar \ Scale down by 64 + bx ax add \ Add to Y + + 0< if ax ax xor then \ Clip to 0 + d# 255 # ax cmp > if d# 255 # ax mov then \ Clip to 255 + + al stos \ Output R + + d# -46 # 4 [sp] ax imul-imm \ Multiply Cr by -0.714 * 64 (actually -0.719) + d# 6 # ax sar \ Scale down by 64 + ax dx mov + d# -22 # 0 [sp] ax imul-imm \ Multiply Cr by -0.344 * 64 (actually -0.344) + d# 6 # ax sar \ Scale down by 64 + dx ax add + bx ax add \ Now we have G + + 0< if ax ax xor then \ Clip to 0 + d# 255 # ax cmp > if d# 255 # ax mov then \ Clip to 255 + + al stos \ Output G + + d# 113 # 0 [sp] ax imul-imm \ Multiply Cr by 1.772 * 64 (actually 1.766) + d# 6 # ax sar \ Scale down by 64 + bx ax add \ Add to Y + + 0< if ax ax xor then \ Clip to 0 + d# 255 # ax cmp > if d# 255 # ax mov then \ Clip to 255 + + al stos \ Output B + d# 255 # al mov + al stos \ Output A + + 8 [sp] dec + 0= until + + d# 12 [sp] sp lea \ Clean stack + 0 [sp] di xchg \ Restore EDI + 4 [sp] si xchg \ Restore ESI +c;
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