利用C语言实现函数predict4x4WithModsInH264(pDatOri,pDatPre,sizX,sizY)其中,pDatOri是原始图像的指针,pDatPre是预测图像的指针,sizX和szY是图像的宽和高。函数的行为是:将图像划分成若干个4x4块然后针对每个块,都在H264的4x4预测模式中选择最佳的模式并基于原始像素进行预测
时间: 2024-02-17 20:05:37 浏览: 23
好的,这是一个图像压缩中的预测函数,具体实现如下:
```c
void predict4x4WithModsInH264(uint8_t *pDatOri, uint8_t *pDatPre, int sizX, int sizY) {
int i, j;
int blockCountX = sizX / 4;
int blockCountY = sizY / 4;
for (i = 0; i < blockCountY; i++) {
for (j = 0; j < blockCountX; j++) {
int oriPos = (i * sizX + j) * 4;
int prePos = oriPos;
int bestMode = 0;
int bestSAD = INT_MAX;
int mode, k, l;
uint8_t *pOri = pDatOri + oriPos;
uint8_t *pPre = pDatPre + prePos;
for (mode = 0; mode < 9; mode++) {
int SAD = 0;
for (k = 0; k < 4; k++) {
for (l = 0; l < 4; l++) {
int pred = 0;
switch (mode) {
case 0:
pred = pPre[-1];
break;
case 1:
pred = pPre[-sizX];
break;
case 2:
pred = (pPre[-1] + pPre[-sizX] + 1) >> 1;
break;
case 3:
pred = (pPre[-2] + 2 * pPre[-1] + pPre[-sizX] + 2) >> 2;
break;
case 4:
pred = (pPre[-2 * sizX] + pPre[-sizX] + 1) >> 1;
break;
case 5:
pred = (pPre[-2 * sizX] + 2 * pPre[-sizX] + pPre[-1] + 2) >> 2;
break;
case 6:
pred = (pPre[-2 * sizX] + pPre[-1] + 1) >> 1;
break;
case 7:
pred = (pPre[-2 * sizX] + 2 * pPre[-1] + pPre[-sizX] + 2) >> 2;
break;
case 8:
pred = (pPre[-3 * sizX] + pPre[-2 * sizX] + pPre[-sizX] + pPre[-1] + 2) >> 2;
break;
}
SAD += abs(pOri[l] - pred);
pPre[l] = pOri[l];
}
pOri += sizX;
pPre += sizX;
}
if (SAD < bestSAD) {
bestSAD = SAD;
bestMode = mode;
}
pOri = pDatOri + oriPos;
pPre = pDatPre + prePos;
}
pOri = pDatOri + oriPos;
pPre = pDatPre + prePos;
for (k = 0; k < 4; k++) {
for (l = 0; l < 4; l++) {
int pred = 0;
switch (bestMode) {
case 0:
pred = pPre[-1];
break;
case 1:
pred = pPre[-sizX];
break;
case 2:
pred = (pPre[-1] + pPre[-sizX] + 1) >> 1;
break;
case 3:
pred = (pPre[-2] + 2 * pPre[-1] + pPre[-sizX] + 2) >> 2;
break;
case 4:
pred = (pPre[-2 * sizX] + pPre[-sizX] + 1) >> 1;
break;
case 5:
pred = (pPre[-2 * sizX] + 2 * pPre[-sizX] + pPre[-1] + 2) >> 2;
break;
case 6:
pred = (pPre[-2 * sizX] + pPre[-1] + 1) >> 1;
break;
case 7:
pred = (pPre[-2 * sizX] + 2 * pPre[-1] + pPre[-sizX] + 2) >> 2;
break;
case 8:
pred = (pPre[-3 * sizX] + pPre[-2 * sizX] + pPre[-sizX] + pPre[-1] + 2) >> 2;
break;
}
pPre[l] = pred;
pOri[l] -= pred;
}
pOri += sizX;
pPre += sizX;
}
}
}
}
```
该函数中,通过循环将图像划分为若干个4x4的块,对于每个块,选择最佳的预测模式,进行预测。其中,预测模式有9种,分别对应H264标准中的4x4预测模式,具体的实现可以参考H264标准文档。预测使用的是原始像素和预测像素之间的SAD(Sum of Absolute Differences)进行衡量,SAD越小,代表预测效果越好。
最后,将预测值和原始像素进行差值,得到残差,以便于后续的压缩编码。