如何为 android 前置摄像头实现 Mirror by libyuv::I420Scale?
How to implement the Mirror by libyuv::I420Scale for android front camera?
以下文字来自libyuv#rotation
Mirror - Horizontal Flip
Mirror functions for horizontally flipping an image, which can be useful for 'self view' of a webcam.
int I420Mirror(const uint8* src_y, int src_stride_y,
const uint8* src_u, int src_stride_u,
const uint8* src_v, int src_stride_v,
uint8* dst_y, int dst_stride_y,
uint8* dst_u, int dst_stride_u,
uint8* dst_v, int dst_stride_v,
int width, int height);
Mirror functionality can also be achieved with the I420Scale and ARGBScale functions by passing negative width and/or height.
但是,我看到 I420Scale
的实现是这样的:
LIBYUV_API
int I420Scale(const uint8* src_y, int src_stride_y,
const uint8* src_u, int src_stride_u,
const uint8* src_v, int src_stride_v,
int src_width, int src_height,
uint8* dst_y, int dst_stride_y,
uint8* dst_u, int dst_stride_u,
uint8* dst_v, int dst_stride_v,
int dst_width, int dst_height,
enum FilterMode filtering) {
int src_halfwidth = SUBSAMPLE(src_width, 1, 1);
int src_halfheight = SUBSAMPLE(src_height, 1, 1);
int dst_halfwidth = SUBSAMPLE(dst_width, 1, 1);
int dst_halfheight = SUBSAMPLE(dst_height, 1, 1);
if (!src_y || !src_u || !src_v || src_width == 0 || src_height == 0 ||
src_width > 32768 || src_height > 32768 ||
!dst_y || !dst_u || !dst_v || dst_width <= 0 || dst_height <= 0) {
return -1;
}
ScalePlane(src_y, src_stride_y, src_width, src_height,
dst_y, dst_stride_y, dst_width, dst_height,
filtering);
ScalePlane(src_u, src_stride_u, src_halfwidth, src_halfheight,
dst_u, dst_stride_u, dst_halfwidth, dst_halfheight,
filtering);
ScalePlane(src_v, src_stride_v, src_halfwidth, src_halfheight,
dst_v, dst_stride_v, dst_halfwidth, dst_halfheight,
filtering);
return 0;
}
如果dst_width <= 0 || dst_height <= 0
,则return -1
;
这是关于 Mirror functionality can also be achieved with the I420Scale by passing negative width and/or height
的笑话吗?
I420Scale
如何实现镜像功能?
我按如下方式操作后对我来说效果很好:
if (facing == 1) {
// front camera should be mirror
src_w = - src_w;
}
if ((ret = I420Scale(
pTempY, src_stride_y,
pTempU, src_stride_u,
pTempV, src_stride_v,
src_w, src_h,
pDstY, dst_width,
pDstU, (dst_width + 1) >> 1,
pDstV, (dst_width + 1) >> 1,
dst_w, dst_h,
kFilterNone
))) {}
以下文字来自libyuv#rotation
Mirror - Horizontal Flip Mirror functions for horizontally flipping an image, which can be useful for 'self view' of a webcam.
int I420Mirror(const uint8* src_y, int src_stride_y,
const uint8* src_u, int src_stride_u,
const uint8* src_v, int src_stride_v,
uint8* dst_y, int dst_stride_y,
uint8* dst_u, int dst_stride_u,
uint8* dst_v, int dst_stride_v,
int width, int height);
Mirror functionality can also be achieved with the I420Scale and ARGBScale functions by passing negative width and/or height.
但是,我看到 I420Scale
的实现是这样的:
LIBYUV_API
int I420Scale(const uint8* src_y, int src_stride_y,
const uint8* src_u, int src_stride_u,
const uint8* src_v, int src_stride_v,
int src_width, int src_height,
uint8* dst_y, int dst_stride_y,
uint8* dst_u, int dst_stride_u,
uint8* dst_v, int dst_stride_v,
int dst_width, int dst_height,
enum FilterMode filtering) {
int src_halfwidth = SUBSAMPLE(src_width, 1, 1);
int src_halfheight = SUBSAMPLE(src_height, 1, 1);
int dst_halfwidth = SUBSAMPLE(dst_width, 1, 1);
int dst_halfheight = SUBSAMPLE(dst_height, 1, 1);
if (!src_y || !src_u || !src_v || src_width == 0 || src_height == 0 ||
src_width > 32768 || src_height > 32768 ||
!dst_y || !dst_u || !dst_v || dst_width <= 0 || dst_height <= 0) {
return -1;
}
ScalePlane(src_y, src_stride_y, src_width, src_height,
dst_y, dst_stride_y, dst_width, dst_height,
filtering);
ScalePlane(src_u, src_stride_u, src_halfwidth, src_halfheight,
dst_u, dst_stride_u, dst_halfwidth, dst_halfheight,
filtering);
ScalePlane(src_v, src_stride_v, src_halfwidth, src_halfheight,
dst_v, dst_stride_v, dst_halfwidth, dst_halfheight,
filtering);
return 0;
}
如果dst_width <= 0 || dst_height <= 0
,则return -1
;
这是关于 Mirror functionality can also be achieved with the I420Scale by passing negative width and/or height
的笑话吗?
I420Scale
如何实现镜像功能?
我按如下方式操作后对我来说效果很好:
if (facing == 1) {
// front camera should be mirror
src_w = - src_w;
}
if ((ret = I420Scale(
pTempY, src_stride_y,
pTempU, src_stride_u,
pTempV, src_stride_v,
src_w, src_h,
pDstY, dst_width,
pDstU, (dst_width + 1) >> 1,
pDstV, (dst_width + 1) >> 1,
dst_w, dst_h,
kFilterNone
))) {}