背景
美术给出一套资源后，可以通过改变图片色相，复用同一套资源产生出多套资源的效果：
上图中蓝色是原始图片，利用代码改变图片色相后，可以产生效果差异明显的资源出来。像一些传统的游戏，如星际争霸等，都是通过这种技术实现了同一兵种，不同颜色种族的特效。
实现理论原理
看上去非常神奇的转换，实际上是利用了HSV格式图像处理的技术：
传统RGB模型：RGB是一种加色模式 将不同比例的RED/GREEN/BLUE混合在一起得到新的颜色
HSV(HSB)模型：通过色相/饱和度/亮度来得到颜色
H(hue):色相 表示颜色的类型 值域[0,360]
S(Saturation):饱和度 从灰度到纯色 值域[0,1]
V(Value or Brightness):亮度 从黑色到特定饱和度的颜色 值域[0,1]
HSV模型图
RGB到HSV的转换公式
HSV到RGB的转换公式
公式可以参考
http://baike.baidu.com/subview/541362/8445478.htm?fr=aladdin
普通代码实现
利用上述转换公式，实现代码如下（透明像素不处理）：
@H_502_82@
<spanstyle="font-family:SimSun;font-size:14px;">Texture2D*HelloWorld::initTextureWithImage(Image*image,float_fhue)
{
unsignedchar*tempData=NULL;
boolhasAlpha=image->hasAlpha();
SizeimageSize=Size((float)(image->getWidth()),(float)(image->getHeight()));
Texture2D::PixelFormatpixelFormat;
unsignedintwidth=image->getWidth();
unsignedintheight=image->getHeight();
//Repackthepixeldataintotherightformat
unsignedintlength=width*height;
unsignedintnewDataLen=0;
//Convert"RRRRRRRRRGGGGGGGGBBBBBBBBAAAAAAAA"to"RRRRRRRRGGGGGGGGBBBBBBBB"
float_f=_fhue/60;//节省运算
if(hasAlpha)
{
//computepixelformat
pixelFormat=Texture2D::PixelFormat::RGBA8888;
tempData=newunsignedchar[length*4];
newDataLen=length*4;
unsignedchar*outPixel8=tempData;
unsignedint*inPixel32=(unsignedint*)image->getData();
for(unsignedinti=0;i<length;++i,++inPixel32)
{
unsignedchar*_colRGB=outPixel8;
*outPixel8++=(*inPixel32>>0)&0xFF;//R
*outPixel8++=(*inPixel32>>8)&0xFF;//G
*outPixel8++=(*inPixel32>>16)&0xFF;//B
*outPixel8=(*inPixel32>>24)&0xFF;//A
//透明图层不做处理
if(*outPixel8++)
{
unsignedchar_r=*_colRGB;
unsignedchar_g=*(_colRGB+1);
unsignedchar_b=*(_colRGB+2);
unsignedcharmin=(_r<_g)?_r:_g;
min=(min<_b)?min:_b;
unsignedcharmax=(_r>_g)?_r:_g;
max=(max>_b)?max:_b;
unsignedchartemp=(max-min);
floathsbH=0;//temp
if(temp)
{
if(max==_r){
if(_g>=_b)
{
hsbH=(float)(_g-_b)/(float)temp;
}
else
{
hsbH=((float)(_g-_b)/(float)temp)+6;
}
}
elseif(max==_g){
hsbH=((float)(_b-_r)/(float)temp)+2;
}
elseif(max==_b){
hsbH=((float)(_r-_g)/(float)temp)+4;
}
}
else
{
hsbH=0;
}
hsbH+=_f;
if(hsbH<0)
hsbH+=6;
elseif(hsbH>6)
hsbH-=6;
chari=(int)hsbH;
hsbH=hsbH-i;
switch(i){
case6:
case0:
(*_colRGB++)=max;
(*_colRGB++)=min+(int)(hsbH*temp);
(*_colRGB++)=min;
break;
case1:
(*_colRGB++)=max-(int)(hsbH*temp);
(*_colRGB++)=max;
(*_colRGB++)=min;
break;
case2:
(*_colRGB++)=min;
(*_colRGB++)=max;
(*_colRGB++)=min+(int)(hsbH*temp);
break;
case3:
(*_colRGB++)=min;
(*_colRGB++)=max-(int)(hsbH*temp);
(*_colRGB++)=max;
break;
case4:
(*_colRGB++)=min+(int)(hsbH*temp);
(*_colRGB++)=min;
(*_colRGB++)=max;
break;
case5:
(*_colRGB++)=max;
(*_colRGB++)=min;
(*_colRGB++)=max-(int)(hsbH*temp);
break;
default:
break;
}
}
}
}
else
{
pixelFormat=Texture2D::PixelFormat::RGB888;
tempData=newunsignedchar[length*3];
newDataLen=length*3;
unsignedchar*out3=image->getData();
unsignedchar*outPixel8=tempData;
for(unsignedinti=0;i<length;++i)
{
unsignedchar_r=*out3++;
unsignedchar_g=*out3++;
unsignedchar_b=*out3++;
//changeHSLForRgb(255,0);
//unsignedchar*_nowRGB=changeHSLForRgb(_r,_g,_b,_fhue);
//_r=*_nowRGB++;
//_g=*_nowRGB++;
//_b=*_nowRGB++;
*outPixel8++=_r;//R
*outPixel8++=_g;//G
*outPixel8++=_b;//B
}
}
Texture2D*_text2d=newTexture2D();
_text2d->initWithData(tempData,newDataLen,pixelFormat,width,height,imageSize);
delete[]tempData;
//_text2d->_hasPremultipliedAlpha=image->hasPremultipliedAlpha();
return_text2d;
}</span>
利用Shader实现
Shader可以利用GPU提升渲染效率：
colorHSL.fsh
@H_502_82@
#ifdefGL_ES
precisionmediumpfloat;
#endif
varyingvec2v_texCoord;
uniformsampler2DCC_Texture0;
uniformfloatu_dH;
uniformfloatu_dS;
uniformfloatu_dL;
voidmain(){
vec4texColor=texture2D(CC_Texture0,v_texCoord);
floatr=texColor.r;
floatg=texColor.g;
floatb=texColor.b;
floata=texColor.a;
//convertrgbtohsl
floath;
floats;
floatl;
{
floatmax=max(max(r,g),b);
floatmin=min(min(r,b);
//----h
if(max==min){
h=0.0;
}elseif(max==r&&g>=b){
h=60.0*(g-b)/(max-min)+0.0;
}elseif(max==r&&g<b){
h=60.0*(g-b)/(max-min)+360.0;
}elseif(max==g){
h=60.0*(b-r)/(max-min)+120.0;
}elseif(max==b){
h=60.0*(r-g)/(max-min)+240.0;
}
//----l
l=0.5*(max+min);
//----s
if(l==0.0||max==min){
s=0.0;
}elseif(0.0<=l&&l<=0.5){
s=(max-min)/(2.0*l);
}elseif(l>0.5){
s=(max-min)/(2.0-2.0*l);
}
}
//(h,s,l)+(dH,dS,dL)->(h,l)
h=h+u_dH;
s=min(1.0,max(0.0,s+u_dS));
l=l+u_dL;
//convert(h,l)torgbandgotfinalcolor
vec4finalColor;
{
floatq;
if(l<0.5){
q=l*(1.0+s);
}elseif(l>=0.5){
q=l+s-l*s;
}
floatp=2.0*l-q;
floathk=h/360.0;
floatt[3];
t[0]=hk+1.0/3.0;t[1]=hk;t[2]=hk-1.0/3.0;
for(inti=0;i<3;i++){
if(t[i]<0.0)t[i]+=1.0;
if(t[i]>1.0)t[i]-=1.0;
}//gott[i]
floatc[3];
for(inti=0;i<3;i++){
if(t[i]<1.0/6.0){
c[i]=p+((q-p)*6.0*t[i]);
}elseif(1.0/6.0<=t[i]&&t[i]<0.5){
c[i]=q;
}elseif(0.5<=t[i]&&t[i]<2.0/3.0){
c[i]=p+((q-p)*6.0*(2.0/3.0-t[i]));
}else{
c[i]=p;
}
}
finalColor=vec4(c[0],c[1],c[2],a);
}
finalColor+=vec4(u_dL,u_dL,0.0);
gl_FragColor=finalColor;
}
以下适用COCOS2.2版本
@H_502_82@
voidsetHSLMode();
voidsetHSL(floath,floats,floatl);
voidupdateHSL();
floatm_dH;
floatm_dS;
floatm_dL;
GLuintm_dHlocation;
GLuintm_dSlocation;
GLuintm_dLlocation;
具体实现
@H_502_82@
voidGameColorSprite::setHSLMode(){
ccBlendFuncblendFunc={GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA};
this->setBlendFunc(blendFunc);
GLchar*fragSource=(GLchar*)CCString::createWithContentsOfFile(CCFileUtils::sharedFileUtils()->fullPathForFilename("colorHSL.fsh").c_str())->getCString();
CGLProgramWithUnifos*pProgram=newCGLProgramWithUnifos();
pProgram->initWithVertexShaderByteArray(ccPositionTextureColor_vert,fragSource);
this->setShaderProgram(pProgram);
pProgram->release();
CHECK_GL_ERROR_DEBUG();
this->getShaderProgram()->addAttribute(kCCAttributeNamePosition,kCCVertexAttrib_Position);
this->getShaderProgram()->addAttribute(kCCAttributeNameColor,kCCVertexAttrib_Color);
this->getShaderProgram()->addAttribute(kCCAttributeNameTexCoord,kCCVertexAttrib_TexCoords);
CHECK_GL_ERROR_DEBUG();
this->getShaderProgram()->link();
CHECK_GL_ERROR_DEBUG();
this->getShaderProgram()->updateUniforms();
CHECK_GL_ERROR_DEBUG();
m_dHlocation=glGetUniformLocation(getShaderProgram()->getProgram(),"u_dH");
m_dSlocation=glGetUniformLocation(getShaderProgram()->getProgram(),"u_dS");
m_dLlocation=glGetUniformLocation(getShaderProgram()->getProgram(),"u_dL");
updateHSL();
}
@H_502_82@
voidGameColorSprite::updateHSL(){
glUniform1f(m_dHlocation,m_dH);
glUniform1f(m_dSlocation,m_dS);
glUniform1f(m_dLlocation,m_dL);
}
