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。
1 void yuv420_2_rgb8888(uint8_t *dst_ptr_, 2 const uint8_t *y_ptr, 3 const uint8_t *u_ptr, 4 const uint8_t *v_ptr, 5 int32_t width, 6 int32_t height) 7 { 8 uint32_t *tables = yuv2rgb565_table; 9 uint32_t *dst_ptr = (uint32_t *)(void *)dst_ptr_; 10 int32_t y_span = width; 11 int32_t uv_span = width>>1; 12 int32_t dst_span = width<<2; 13 dst_span >>= 2; 14 15 height -= 1; 16 while (height > 0) 17 { 18 height -= width<<16; 19 height += 1<<16; 20 while (height < 0) 21 { 22 /* Do 2 column pairs */ 23 uint32_t uv, y0, y1; 24 25 uv = READUV(*u_ptr++,*v_ptr++); 26 y1 = uv + READY(y_ptr[y_span]); 27 y0 = uv + READY(*y_ptr++); 28 FIXUP(y1); 29 FIXUP(y0); 30 STORE(y1, dst_ptr[dst_span]); 31 STORE(y0, *dst_ptr++); 32 y1 = uv + READY(y_ptr[y_span]); 33 y0 = uv + READY(*y_ptr++); 34 FIXUP(y1); 35 FIXUP(y0); 36 STORE(y1, dst_ptr[dst_span]); 37 STORE(y0, *dst_ptr++); 38 height += (2<<16); 39 } 40 if ((height>>16) == 0) 41 { 42 /* Trailing column pair */ 43 uint32_t uv, y0, y1; 44 45 uv = READUV(*u_ptr,*v_ptr); 46 y1 = uv + READY(y_ptr[y_span]); 47 y0 = uv + READY(*y_ptr++); 48 FIXUP(y1); 49 FIXUP(y0); 50 STORE(y0, dst_ptr[dst_span]); 51 STORE(y1, *dst_ptr++); 52 } 53 dst_ptr += dst_span*2-width; 54 y_ptr += y_span*2-width; 55 u_ptr += uv_span-(width>>1); 56 v_ptr += uv_span-(width>>1); 57 height = (height<<16)>>16; 58 height -= 2; 59 } 60 if (height == 0) 61 { 62 /* Trail row */ 63 height -= width<<16; 64 height += 1<<16; 65 while (height < 0) 66 { 67 /* Do a row pair */ 68 uint32_t uv, y0, y1; 69 70 uv = READUV(*u_ptr++,*v_ptr++); 71 y1 = uv + READY(*y_ptr++); 72 y0 = uv + READY(*y_ptr++); 73 FIXUP(y1); 74 FIXUP(y0); 75 STORE(y1, *dst_ptr++); 76 STORE(y0, *dst_ptr++); 77 height += (2<<16); 78 } 79 if ((height>>16) == 0) 80 { 81 /* Trailing pix */ 82 uint32_t uv, y0; 83 84 uv = READUV(*u_ptr++,*v_ptr++); 85 y0 = uv + READY(*y_ptr++); 86 FIXUP(y0); 87 STORE(y0, *dst_ptr++); 88 } 89 } 90 }
数据表
yuv2rgb565_table
/* 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, 0xFC90D800U, 0xFC70E800U, 0xFC30F000U, 0xFBF10000U, 0xFBD11000U, 0xFB911800U, 0xFB712800U, 0xFB313000U, 0xFAF14000U, 0xFAD14800U, 0xFA915800U, 0xFA516800U, 0xFA317000U, 0xF9F18000U, 0xF9D18800U, 0xF9919800U, 0xF951A800U, 0xF931B000U, 0xF8F1C000U, 0xF8B1C800U, 0xF891D800U, 0xF851E800U, 0xF831F000U, 0xF7F20000U, 0xF7B20800U, 0xF7921800U, 0xF7522800U, 0xF7123000U, 0xF6F24000U, 0xF6B24800U, 0xF6925800U, 0xF6526800U, 0xF6127000U, 0xF5F28000U, 0xF5B28800U, 0xF5729800U, 0xF552A800U, 0xF512B000U, 0xF4F2C000U, 0xF4B2C800U, 0xF472D800U, 0xF452E800U, 0xF412F000U, 0xF3D30000U, 0xF3B30800U, 0xF3731800U, 0xF3532800U, 0xF3133000U, 0xF2D34000U, 0xF2B34800U, 0xF2735800U, 0xF2336800U, 0xF2137000U, 0xF1D38000U, 0xF1B38800U, 0xF1739800U, 0xF133A800U, 0xF113B000U, 0xF0D3C000U, 0xF093C800U, 0xF073D800U, 0xF033E000U, 0xF013F000U, 0xEFD40000U, 0xEF940800U, 0xEF741800U, 0xEF342000U, 0xEEF43000U, 0xEED44000U, 0xEE944800U, 0xEE745800U, 0xEE346000U, 0xEDF47000U, 0xEDD48000U, 0xED948800U, 0xED549800U, 0xED34A000U, 0xECF4B000U, 0xECD4C000U, 0xEC94C800U, 0xEC54D800U, 0xEC34E000U, 0xEBF4F000U, 0xEBB50000U, 0xEB950800U, 0xEB551800U, 0xEB352000U, 0xEAF53000U, 0xEAB54000U, 0xEA954800U, 0xEA555800U, 0xEA156000U, 0xE9F57000U, 0xE9B58000U, 0xE9958800U, 0xE9559800U, 0xE915A000U, 0xE8F5B000U, 0xE8B5C000U, 0xE875C800U, 0xE855D800U, 0xE815E000U, 0xE7F5F000U, 0xE7B60000U, 0xE7760800U, 0xE7561800U, 0xE7162000U, 0xE6D63000U, 0xE6B64000U, 0xE6764800U, 0xE6365800U };
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