调节像素偏移
调节像素偏移主要是用来处理瘦脸大眼、调节下巴等处理。前面我们做了图像三角剖分和重建工作，得到了整张人脸的索引。接下来我们只需要得到对应的顶点坐标、纹理坐标，更新顶点坐标缓冲、纹理坐标缓冲即可。这里需要根据是否有人脸来做顶点判断。其中updateCartesianVertices()方法是用来传递人脸关键点在图像中的实际笛卡尔坐标的，这里主要是为了方便做像素偏移计算：
if (LandmarkEngine.getInstance().hasFace()) {
LandmarkEngine.getInstance().updateFaceAdjustPoints(mVertices, mTextureVertices, 0);
mVertexBuffer.clear();
mVertexBuffer.put(mVertices);
mVertexBuffer.position(0);
mTextureBuffer.clear();
mTextureBuffer.put(mTextureVertices);
mTextureBuffer.position(0);
updateCartesianVertices();
mIndexBuffer.clear();
mIndexBuffer.put(FaceImageIndices);
mIndexBuffer.position(0);
mIndexLength = mIndexBuffer.capacity();
setInteger(mEnableReshapeHandle, 1);
} else { // 没有人脸时索引变回默认的6个
mIndexBuffer.clear();
mIndexBuffer.put(TextureRotationUtils.Indices);
mIndexBuffer.position(0);
mIndexLength = 6;
setInteger(mEnableReshapeHandle, 0);
}
接下来，我们就可以在fragment shader 中进行像素调节处理了。关于像素偏移调节，可以参考下面这篇文章，写得比较详细：
脸型调节的fragment shader 如下所示(截止本文章位置，部分脸型调节功能还没完成)
precision mediump float;
varying vec2 textureCoordinate;
uniform sampler2D inputTexture;
// 图像笛卡尔坐标系的关键点，也就是纹理坐标乘以宽高得到
uniform vec2 cartesianPoints[106];
#define INDEX_FACE_LIFT 0 // 瘦脸
#define INDEX_FACE_SHAVE 1 // 削脸
#define INDEX_FACE_NARROW 2 // 小脸
#define INDEX_CHIN 3 // 下巴
#define INDEX_FOREHEAD 4 // 额头
#define INDEX_EYE_ENLARGE 5 // 大眼
#define INDEX_EYE_DISTANCE 6 // 眼距
#define INDEX_EYE_CORNER 7 // 眼角
#define INDEX_NOSE_THIN 8 // 瘦鼻
#define INDEX_ALAE 9 // 鼻翼
#define INDEX_PROBOSCIS 10 // 长鼻
#define INDEX_MOUTH 11 // 嘴型
#define INDEX_SIZE 12 // 索引大小
// 美型程度参数列表
uniform float reshapeIntensity[INDEX_SIZE];
// 纹理宽度
uniform int textureWidth;
// 纹理高度
uniform int textureHeight;
// 是否允许美型处理，存在人脸时为1，没有人脸时为0
uniform int enableReshape;
// 曲线形变处理
vec2 curveWarp(vec2 textureCoord, vec2 originPosition, vec2 targetPosition, float radius)
{
vec2 offset = vec2(0.0);
vec2 result = vec2(0.0);
vec2 direction = targetPosition - originPosition;
float infect = distance(textureCoord, originPosition)/radius;
infect = 1.0 - infect;
infect = clamp(infect, 0.0, 1.0);
offset = direction * infect;
result = textureCoord - offset;
return result;
}
// 大眼处理
vec2 enlargeEye(vec2 currentCoordinate, vec2 circleCenter, float radius, float intensity)
{
float currentDistance = distance(currentCoordinate, circleCenter);
float weight = currentDistance / radius;
weight = 1.0 - intensity * (1.0 - weight * weight);
weight = clamp(weight, 0.0, 1.0);
currentCoordinate = circleCenter + (currentCoordinate - circleCenter) * weight;
return currentCoordinate;
}
// 瘦脸
vec2 faceLift(vec2 currentCoordinate, float faceLength)
{
vec2 coordinate = currentCoordinate;
vec2 currentPoint = vec2(0.0);
vec2 destPoint = vec2(0.0);
float faceLiftScale = reshapeIntensity[INDEX_FACE_LIFT] * 0.05;
float radius = faceLength;
currentPoint = cartesianPoints[3];
destPoint = currentPoint + (cartesianPoints[44] - currentPoint) * faceLiftScale;
coordinate = curveWarp(coordinate, currentPoint, destPoint, radius);
currentPoint = cartesianPoints[29];
destPoint = currentPoint + (cartesianPoints[44] - currentPoint) * faceLiftScale;
coordinate = curveWarp(coordinate, currentPoint, destPoint, radius);
radius = faceLength * 0.8;
currentPoint = cartesianPoints[10];
destPoint = currentPoint + (cartesianPoints[46] - currentPoint) * (faceLiftScale * 0.6);
coordinate = curveWarp(coordinate, currentPoint, destPoint, radius);
currentPoint = cartesianPoints[22];
destPoint = currentPoint + (cartesianPoints[46] - currentPoint) * (faceLiftScale * 0.6);
coordinate = curveWarp(coordinate, currentPoint, destPoint, radius);
return coordinate;
}
// 削脸
vec2 faceShave(vec2 currentCoordinate, float faceLength)
{
vec2 coordinate = currentCoordinate;
vec2 currentPoint = vec2(0.0);
vec2 destPoint = vec2(0.0);
float faceShaveScale = reshapeIntensity[INDEX_FACE_SHAVE] * 0.12;
float radius = faceLength * 1.0;
// 下巴中心
vec2 chinCenter = (cartesianPoints[16] + cartesianPoints[93]) * 0.5;
currentPoint = cartesianPoints[13];
destPoint = currentPoint + (chinCenter - currentPoint) * faceShaveScale;
coordinate = curveWarp(coordinate, currentPoint, destPoint, radius);
currentPoint = cartesianPoints[19];
destPoint = currentPoint + (chinCenter - currentPoint) * faceShaveScale;
coordinate = curveWarp(coordinate, currentPoint, destPoint, radius);
return coordinate;
}
// 处理下巴
vec2 chinChange(vec2 currentCoordinate, float faceLength)
{
vec2 coordinate = currentCoordinate;
vec2 currentPoint = vec2(0.0);
vec2 destPoint = vec2(0.0);
float chinScale = reshapeIntensity[INDEX_CHIN] * 0.08;
float radius = faceLength * 1.25;
currentPoint = cartesianPoints[16];
destPoint = currentPoint + (cartesianPoints[46] - currentPoint) * chinScale;
coordinate = curveWarp(coordinate, currentPoint, destPoint, radius);
return coordinate;
}
void main()
{
vec2 coordinate = textureCoordinate.xy;
// 禁用美型处理或者鼻子不在图像中，则直接绘制
if (enableReshape == 0 || (cartesianPoints[46].x / float(textureWidth) <= 0.03)
|| (cartesianPoints[46].y / float(textureHeight)) <= 0.03) {
gl_FragColor = texture2D(inputTexture, coordinate);
return;
}
// 将坐标转成图像大小，这里是为了方便计算
coordinate = textureCoordinate * vec2(float(textureWidth), float(textureHeight));
float eyeDistance = distance(cartesianPoints[74], cartesianPoints[77]); // 两个瞳孔的距离
// 瘦脸
coordinate = faceLift(coordinate, eyeDistance);
// 削脸
coordinate = faceShave(coordinate, eyeDistance);
// 小脸 TODO 眼睛到下巴图像线性缩小
// 下巴
coordinate = chinChange(coordinate, eyeDistance);
// 额头
// 大眼
float eyeEnlarge = reshapeIntensity[INDEX_EYE_ENLARGE] * 0.12; // 放大倍数
if (eyeEnlarge > 0.0) {
float radius = eyeDistance * 0.33; // 眼睛放大半径
coordinate = enlargeEye(coordinate, cartesianPoints[74] + (cartesianPoints[77] - cartesianPoints[74]) * 0.05, radius, eyeEnlarge);
coordinate = enlargeEye(coordinate, cartesianPoints[77] + (cartesianPoints[74] - cartesianPoints[77]) * 0.05, radius, eyeEnlarge);
}
// 眼距
// 眼角
// 瘦鼻
// 鼻翼
// 长鼻
// 嘴型
// 转变回原来的纹理坐标系
coordinate = coordinate / vec2(float(textureWidth), float(textureHeight));
// 输出图像
gl_FragColor = texture2D(inputTexture, coordinate);
}
