YUV格式有两大类：planar和packed。planar的YUV格式，先连续存储所有像素点的Y，紧接着存储所有像素点的U，随后是所有像素点的V，这里所讲述的就是这中存储格式的；packed的YUV格式，每个像素点的Y,U,V是连续交叉存储的。
色彩空间转换主要有三种方法，1、整点运算，即通过公式对每个点进行计算，速度超慢，基本只有在PC下才能够运行；2、查表法，即由由YUV直接查表得到对应的RGB值；3、通过汇编指令,可参考http://blog.csdn.net/alien75/article/details/7377179；
本文主要介绍第二种方法，经本人使用测试，第二种方法效率可以满足本人需求，且图片转换后颜色无失真、走样等情况发生，而第一种方法，在网上搜到的很多代码装换效率低不说，转换后的图像颜色都存在很严重的失真现象。
如下代码也是从一开源代码中扣出来的，只是从YUV420转换到RGB32格式，该转换方法在 ARM926EJ-S这种CPU下运算效率还是很高的。
void yuv420_2_rgb8888(uint8_t *dst_ptr_,
const uint8_t *y_ptr,
const uint8_t *u_ptr,
const uint8_t *v_ptr,
int32_t width,
int32_t height)
{
uint32_t *tables = yuv2rgb565_table;
uint32_t *dst_ptr = (uint32_t *)(void *)dst_ptr_;
int32_t y_span = width;
int32_t uv_span = width>>1;
int32_t dst_span = width<<2;
dst_span >>= 2;
height -= 1;
while (height > 0)
{
height -= width<<16;
height += 1<<16;
while (height < 0)
{
/* Do 2 column pairs */
uint32_t uv, y0, y1;
uv = READUV(*u_ptr++,*v_ptr++);
y1 = uv + READY(y_ptr[y_span]);
y0 = uv + READY(*y_ptr++);
FIXUP(y1);
FIXUP(y0);
STORE(y1, dst_ptr[dst_span]);
STORE(y0, *dst_ptr++);
y1 = uv + READY(y_ptr[y_span]);
y0 = uv + READY(*y_ptr++);
FIXUP(y1);
FIXUP(y0);
STORE(y1, dst_ptr[dst_span]);
STORE(y0, *dst_ptr++);
height += (2<<16);
}
if ((height>>16) == 0)
{
/* Trailing column pair */
uint32_t uv, y0, y1;
uv = READUV(*u_ptr,*v_ptr);
y1 = uv + READY(y_ptr[y_span]);
y0 = uv + READY(*y_ptr++);
FIXUP(y1);
FIXUP(y0);
STORE(y0, dst_ptr[dst_span]);
STORE(y1, *dst_ptr++);
}
dst_ptr += dst_span*2-width;
y_ptr += y_span*2-width;
u_ptr += uv_span-(width>>1);
v_ptr += uv_span-(width>>1);
height = (height<<16)>>16;
height -= 2;
}
if (height == 0)
{
/* Trail row */
height -= width<<16;
height += 1<<16;
while (height < 0)
{
/* Do a row pair */
uint32_t uv, y0, y1;
uv = READUV(*u_ptr++,*v_ptr++);
y1 = uv + READY(*y_ptr++);
y0 = uv + READY(*y_ptr++);
FIXUP(y1);
FIXUP(y0);
STORE(y1, *dst_ptr++);
STORE(y0, *dst_ptr++);
height += (2<<16);
}
if ((height>>16) == 0)
{
/* Trailing pix */
uint32_t uv, y0;
uv = READUV(*u_ptr++,*v_ptr++);
y0 = uv + READY(*y_ptr++);
FIXUP(y0);
STORE(y0, *dst_ptr++);
}
}
}数据表
yuv2rgb565_table/* YUV-> RGB conversion code.
*
* Copyright (C) 2011 Robin Watts ([email protected]) for Pinknoise
* Productions Ltd.
*
* Licensed under the BSD license. See 'COPYING' for details of
* (non-)warranty.
*
*/
/* For BREW or Symbian you might need to make this static const rather than
* just const, and introduce a function to get the address. */
enum
{
FLAGS = 0x40080100
};
#define READUV(U,V) (tables[256 + (U)] + tables[512 + (V)])
#define READY(Y) tables[Y]
#define FIXUP(Y) \
do { \
int tmp = (Y) & FLAGS; \
if (tmp != 0) \
{ \
tmp -= tmp>>8; \
(Y) |= tmp; \
tmp = FLAGS & ~(Y>>1); \
(Y) += tmp>>8; \
} \
} while (0 == 1)
#define STORE(Y,DSTPTR) \
do { \
(DSTPTR) = (Y & 0xFF) | (0xFF00 & (Y>>14)) | (0xFF0000 & (Y<<5));\
} while (0 == 1)
const uint32_t yuv2rgb565_table[256*3] =
{
/* y_table */
0x7FFFFFEDU,
0x7FFFFFEFU,
0x7FFFFFF0U,
0x7FFFFFF1U,
0x7FFFFFF2U,
0x7FFFFFF3U,
0x7FFFFFF4U,
0x7FFFFFF6U,
0x7FFFFFF7U,
0x7FFFFFF8U,
0x7FFFFFF9U,
0x7FFFFFFAU,
0x7FFFFFFBU,
0x7FFFFFFDU,
0x7FFFFFFEU,
0x7FFFFFFFU,
0x80000000U,
0x80400801U,
0x80A01002U,
0x80E01803U,
0x81202805U,
0x81803006U,
0x81C03807U,
0x82004008U,
0x82604809U,
0x82A0500AU,
0x82E0600CU,
0x8340680DU,
0x8380700EU,
0x83C0780FU,
0x84208010U,
0x84608811U,
0x84A09813U,
0x8500A014U,
0x8540A815U,
0x8580B016U,
0x85E0B817U,
0x8620C018U,
0x8660D01AU,
0x86C0D81BU,
0x8700E01CU,
0x8740E81DU,
0x87A0F01EU,
0x87E0F81FU,
0x88210821U,
0x88811022U,
0x88C11823U,
0x89012024U,
0x89412825U,
0x89A13026U,
0x89E14028U,
0x8A214829U,
0x8A81502AU,
0x8AC1582BU,
0x8B01602CU,
0x8B61682DU,
0x8BA1782FU,
0x8BE18030U,
0x8C418831U,
0x8C819032U,
0x8CC19833U,
0x8D21A034U,
0x8D61B036U,
0x8DA1B837U,
0x8E01C038U,
0x8E41C839U,
0x8E81D03AU,
0x8EE1D83BU,
0x8F21E83DU,
0x8F61F03EU,
0x8FC1F83FU,
0x90020040U,
0x90420841U,
0x90A21042U,
0x90E22044U,
0x91222845U,
0x91823046U,
0x91C23847U,
0x92024048U,
0x92624849U,
0x92A2504AU,
0x92E2604CU,
0x9342684DU,
0x9382704EU,
0x93C2784FU,
0x94228050U,
0x94628851U,
0x94A29853U,
0x9502A054U,
0x9542A855U,
0x9582B056U,
0x95E2B857U,
0x9622C058U,
0x9662D05AU,
0x96C2D85BU,
0x9702E05CU,
0x9742E85DU,
0x97A2F05EU,
0x97E2F85FU,
0x98230861U,
0x98831062U,
0x98C31863U,
0x99032064U,
0x99632865U,
0x99A33066U,
0x99E34068U,
0x9A434869U,
0x9A83506AU,
0x9AC3586BU,
0x9B23606CU,
0x9B63686DU,
0x9BA3786FU,
0x9BE38070U,
0x9C438871U,
0x9C839072U,
0x9CC39873U,
0x9D23A074U,
0x9D63B076U,
0x9DA3B877U,
0x9E03C078U,
0x9E43C879U,
0x9E83D07AU,
0x9EE3D87BU,
0x9F23E87DU,
0x9F63F07EU,
0x9FC3F87FU,
0xA0040080U,
0xA0440881U,
0xA0A41082U,
0xA0E42084U,
0xA1242885U,
0xA1843086U,
0xA1C43887U,
0xA2044088U,
0xA2644889U,
0xA2A4588BU,
0xA2E4608CU,
0xA344688DU,
0xA384708EU,
0xA3C4788FU,
0xA4248090U,
0xA4649092U,
0xA4A49893U,
0xA504A094U,
0xA544A895U,
0xA584B096U,
0xA5E4B897U,
0xA624C098U,
0xA664D09AU,
0xA6C4D89BU,
0xA704E09CU,
0xA744E89DU,
0xA7A4F09EU,
0xA7E4F89FU,
0xA82508A1U,
0xA88510A2U,
0xA8C518A3U,
0xA90520A4U,
0xA96528A5U,
0xA9A530A6U,
0xA9E540A8U,
0xAA4548A9U,
0xAA8550AAU,
0xAAC558ABU,
0xAB2560ACU,
0xAB6568ADU,
0xABA578AFU,
0xAC0580B0U,
0xAC4588B1U,
0xAC8590B2U,
0xACE598B3U,
0xAD25A0B4U,
0xAD65B0B6U,
0xADA5B8B7U,
0xAE05C0B8U,
0xAE45C8B9U,
0xAE85D0BAU,
0xAEE5D8BBU,
0xAF25E8BDU,
0xAF65F0BEU,
0xAFC5F8BFU,
0xB00600C0U,
0xB04608C1U,
0xB0A610C2U,
0xB0E620C4U,
0xB12628C5U,
0xB18630C6U,
0xB1C638C7U,
0xB20640C8U,
0xB26648C9U,
0xB2A658CBU,
0xB2E660CCU,
0xB34668CDU,
0xB38670CEU,
0xB3C678CFU,
0xB42680D0U,
0xB46690D2U,
0xB4A698D3U,
0xB506A0D4U,
0xB546A8D5U,
0xB586B0D6U,
0xB5E6B8D7U,
0xB626C8D9U,
0xB666D0DAU,
0xB6C6D8DBU,
0xB706E0DCU,
0xB746E8DDU,
0xB7A6F0DEU,
0xB7E6F8DFU,
0xB82708E1U,
0xB88710E2U,
0xB8C718E3U,
0xB90720E4U,
0xB96728E5U,
0xB9A730E6U,
0xB9E740E8U,
0xBA4748E9U,
0xBA8750EAU,
0xBAC758EBU,
0xBB2760ECU,
0xBB6768EDU,
0xBBA778EFU,
0xBC0780F0U,
0xBC4788F1U,
0xBC8790F2U,
0xBCE798F3U,
0xBD27A0F4U,
0xBD67B0F6U,
0xBDC7B8F7U,
0xBE07C0F8U,
0xBE47C8F9U,
0xBEA7D0FAU,
0xBEE7D8FBU,
0xBF27E8FDU,
0xBF87F0FEU,
0xBFC7F8FFU,
0xC0080100U,
0xC0480901U,
0xC0A81102U,
0xC0E82104U,
0xC0E82104U,
0xC0E82104U,
0xC0E82104U,
0xC0E82104U,
0xC0E82104U,
0xC0E82104U,
0xC0E82104U,
0xC0E82104U,
0xC0E82104U,
0xC0E82104U,
0xC0E82104U,
0xC0E82104U,
0xC0E82104U,
0xC0E82104U,
0xC0E82104U,
0xC0E82104U,
/* u_table */
0x0C400103U,
0x0C200105U,
0x0C200107U,
0x0C000109U,
0x0BE0010BU,
0x0BC0010DU,
0x0BA0010FU,
0x0BA00111U,
0x0B800113U,
0x0B600115U,
0x0B400117U,
0x0B400119U,
0x0B20011BU,
0x0B00011DU,
0x0AE0011FU,
0x0AE00121U,
0x0AC00123U,
0x0AA00125U,
0x0A800127U,
0x0A600129U,
0x0A60012BU,
0x0A40012DU,
0x0A20012FU,
0x0A000131U,
0x0A000132U,
0x09E00134U,
0x09C00136U,
0x09A00138U,
0x09A0013AU,
0x0980013CU,
0x0960013EU,
0x09400140U,
0x09400142U,
0x09200144U,
0x09000146U,
0x08E00148U,
0x08C0014AU,
0x08C0014CU,
0x08A0014EU,
0x08800150U,
0x08600152U,
0x08600154U,
0x08400156U,
0x08200158U,
0x0800015AU,
0x0800015CU,
0x07E0015EU,
0x07C00160U,
0x07A00162U,
0x07A00164U,
0x07800166U,
0x07600168U,
0x0740016AU,
0x0720016CU,
0x0720016EU,
0x07000170U,
0x06E00172U,
0x06C00174U,
0x06C00176U,
0x06A00178U,
0x0680017AU,
0x0660017CU,
0x0660017EU,
0x06400180U,
0x06200182U,
0x06000184U,
0x05E00185U,
0x05E00187U,
0x05C00189U,
0x05A0018BU,
0x0580018DU,
0x0580018FU,
0x05600191U,
0x05400193U,
0x05200195U,
0x05200197U,
0x05000199U,
0x04E0019BU,
0x04C0019DU,
0x04C0019FU,
0x04A001A1U,
0x048001A3U,
0x046001A5U,
0x044001A7U,
0x044001A9U,
0x042001ABU,
0x040001ADU,
0x03E001AFU,
0x03E001B1U,
0x03C001B3U,
0x03A001B5U,
0x038001B7U,
0x038001B9U,
0x036001BBU,
0x034001BDU,
0x032001BFU,
0x032001C1U,
0x030001C3U,
0x02E001C5U,
0x02C001C7U,
0x02A001C9U,
0x02A001CBU,
0x028001CDU,
0x026001CFU,
0x024001D1U,
0x024001D3U,
0x022001D5U,
0x020001D7U,
0x01E001D8U,
0x01E001DAU,
0x01C001DCU,
0x01A001DEU,
0x018001E0U,
0x016001E2U,
0x016001E4U,
0x014001E6U,
0x012001E8U,
0x010001EAU,
0x010001ECU,
0x00E001EEU,
0x00C001F0U,
0x00A001F2U,
0x00A001F4U,
0x008001F6U,
0x006001F8U,
0x004001FAU,
0x004001FCU,
0x002001FEU,
0x00000200U,
0xFFE00202U,
0xFFC00204U,
0xFFC00206U,
0xFFA00208U,
0xFF80020AU,
0xFF60020CU,
0xFF60020EU,
0xFF400210U,
0xFF200212U,
0xFF000214U,
0xFF000216U,
0xFEE00218U,
0xFEC0021AU,
0xFEA0021CU,
0xFEA0021EU,
0xFE800220U,
0xFE600222U,
0xFE400224U,
0xFE200226U,
0xFE200228U,
0xFE000229U,
0xFDE0022BU,
0xFDC0022DU,
0xFDC0022FU,
0xFDA00231U,
0xFD800233U,
0xFD600235U,
0xFD600237U,
0xFD400239U,
0xFD20023BU,
0xFD00023DU,
0xFCE0023FU,
0xFCE00241U,
0xFCC00243U,
0xFCA00245U,
0xFC800247U,
0xFC800249U,
0xFC60024BU,
0xFC40024DU,
0xFC20024FU,
0xFC200251U,
0xFC000253U,
0xFBE00255U,
0xFBC00257U,
0xFBC00259U,
0xFBA0025BU,
0xFB80025DU,
0xFB60025FU,
0xFB400261U,
0xFB400263U,
0xFB200265U,
0xFB000267U,
0xFAE00269U,
0xFAE0026BU,
0xFAC0026DU,
0xFAA0026FU,
0xFA800271U,
0xFA800273U,
0xFA600275U,
0xFA400277U,
0xFA200279U,
0xFA20027BU,
0xFA00027CU,
0xF9E0027EU,
0xF9C00280U,
0xF9A00282U,
0xF9A00284U,
0xF9800286U,
0xF9600288U,
0xF940028AU,
0xF940028CU,
0xF920028EU,
0xF9000290U,
0xF8E00292U,
0xF8E00294U,
0xF8C00296U,
0xF8A00298U,
0xF880029AU,
0xF860029CU,
0xF860029EU,
0xF84002A0U,
0xF82002A2U,
0xF80002A4U,
0xF80002A6U,
0xF7E002A8U,
0xF7C002AAU,
0xF7A002ACU,
0xF7A002AEU,
0xF78002B0U,
0xF76002B2U,
0xF74002B4U,
0xF74002B6U,
0xF72002B8U,
0xF70002BAU,
0xF6E002BCU,
0xF6C002BEU,
0xF6C002C0U,
0xF6A002C2U,
0xF68002C4U,
0xF66002C6U,
0xF66002C8U,
0xF64002CAU,
0xF62002CCU,
0xF60002CEU,
0xF60002CFU,
0xF5E002D1U,
0xF5C002D3U,
0xF5A002D5U,
0xF5A002D7U,
0xF58002D9U,
0xF56002DBU,
0xF54002DDU,
0xF52002DFU,
0xF52002E1U,
0xF50002E3U,
0xF4E002E5U,
0xF4C002E7U,
0xF4C002E9U,
0xF4A002EBU,
0xF48002EDU,
0xF46002EFU,
0xF46002F1U,
0xF44002F3U,
0xF42002F5U,
0xF40002F7U,
0xF3E002F9U,
0xF3E002FBU,
/* v_table */
0x1A09A000U,
0x19E9A800U,
0x19A9B800U,
0x1969C800U,
0x1949D000U,
0x1909E000U,
0x18C9E800U,
0x18A9F800U,
0x186A0000U,
0x182A1000U,
0x180A2000U,
0x17CA2800U,
0x17AA3800U,
0x176A4000U,
0x172A5000U,
0x170A6000U,
0x16CA6800U,
0x168A7800U,
0x166A8000U,
0x162A9000U,
0x160AA000U,
0x15CAA800U,
0x158AB800U,
0x156AC000U,
0x152AD000U,
0x14EAE000U,
0x14CAE800U,
0x148AF800U,
0x146B0000U,
0x142B1000U,
0x13EB2000U,
0x13CB2800U,
0x138B3800U,
0x134B4000U,
0x132B5000U,
0x12EB6000U,
0x12CB6800U,
0x128B7800U,
0x124B8000U,
0x122B9000U,
0x11EBA000U,
0x11ABA800U,
0x118BB800U,
0x114BC000U,
0x112BD000U,
0x10EBE000U,
0x10ABE800U,
0x108BF800U,
0x104C0000U,
0x100C1000U,
0x0FEC2000U,
0x0FAC2800U,
0x0F8C3800U,
0x0F4C4000U,
0x0F0C5000U,
0x0EEC5800U,
0x0EAC6800U,
0x0E6C7800U,
0x0E4C8000U,
0x0E0C9000U,
0x0DEC9800U,
0x0DACA800U,
0x0D6CB800U,
0x0D4CC000U,
0x0D0CD000U,
0x0CCCD800U,
0x0CACE800U,
0x0C6CF800U,
0x0C4D0000U,
0x0C0D1000U,
0x0BCD1800U,
0x0BAD2800U,
0x0B6D3800U,
0x0B2D4000U,
0x0B0D5000U,
0x0ACD5800U,
0x0AAD6800U,
0x0A6D7800U,
0x0A2D8000U,
0x0A0D9000U,
0x09CD9800U,
0x098DA800U,
0x096DB800U,
0x092DC000U,
0x090DD000U,
0x08CDD800U,
0x088DE800U,
0x086DF800U,
0x082E0000U,
0x07EE1000U,
0x07CE1800U,
0x078E2800U,
0x076E3800U,
0x072E4000U,
0x06EE5000U,
0x06CE5800U,
0x068E6800U,
0x064E7800U,
0x062E8000U,
0x05EE9000U,
0x05CE9800U,
0x058EA800U,
0x054EB800U,
0x052EC000U,
0x04EED000U,
0x04AED800U,
0x048EE800U,
0x044EF000U,
0x042F0000U,
0x03EF1000U,
0x03AF1800U,
0x038F2800U,
0x034F3000U,
0x030F4000U,
0x02EF5000U,
0x02AF5800U,
0x028F6800U,
0x024F7000U,
0x020F8000U,
0x01EF9000U,
0x01AF9800U,
0x016FA800U,
0x014FB000U,
0x010FC000U,
0x00EFD000U,
0x00AFD800U,
0x006FE800U,
0x004FF000U,
0x00100000U,
0xFFD01000U,
0xFFB01800U,
0xFF702800U,
0xFF303000U,
0xFF104000U,
0xFED05000U,
0xFEB05800U,
0xFE706800U,
0xFE307000U,
0xFE108000U,
0xFDD09000U,
0xFD909800U,
0xFD70A800U,
0xFD30B000U,
0xFD10C000U,
0xFCD0D000U,
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