我正在寻找一种在C / C ++中使用Skia库在EGLTexture上绘制文本的方法。我打算在启动SurfaceFlinger之前运行一个在启动时在Android平台上运行的程序。
请不要指向Android Java示例，因为这不是我想要的。我在帧缓冲级别解决UI问题。我正在寻找一种使用Android原生库（Skia等）在C / C ++中完成此操作的方法。
我有一个示例程序可以使用SkBitmap将图像渲染到EGLTexture上。我能够在显示器上显示它。我按照同样的例子提出了这样的策略。但它不起作用。
0）用绿色清除屏幕
1）创建大小为640x480的SkBitmap
2）创建由SkBitmap.lockPixels（）返回的像素缓冲区支持的EGLTexture
3）使用SkCanvas在SkBitmap上绘制文本。将位图上传到上面的纹理中。
4）然后在当前表面上绘制纹理
我使用启动动画程序（android）作为我的起点。 当我运行这个程序时，我看到的只是绿色。我检查了EGL调用的错误。他们似乎都成功了。谢谢你的帮助
在google群组上发布此问题。谷歌的Brian在这里有一些指示： https://groups.google.com/d/topic/skia-discuss/aC5f6HB4gSU/discussion
以下是实现上述目的的代码。
#define EXPECT_NO_GL_ERROR(stmt) \
do { \
stmt; \
const EGLint error_code = eglGetError(); \
if (EGL_SUCCESS != error_code){ \
LOGD("GLTest: GL error code %d at %s:%d", error_code, __FILE__, __LINE__); \
__android_log_assert("GLTest", "GLtest", "GlTest"); \
}\
} while(0)
struct Texture
{
GLint w;
GLint h;
GLuint id;
};
bool GLTest::frametest()
{
Texture texFrame;
// Paint screen with green color
glShadeModel (GL_FLAT);
glDisable (GL_DITHER);
glDisable (GL_SCISSOR_TEST);
glClearColor(0, 1, 0, 1);
glClear (GL_COLOR_BUFFER_BIT);
eglSwapBuffers(mDisplay, mSurface);
SkGraphics::Init();
SkBitmap bitmap;
bitmap.setConfig(SkBitmap::kARGB_8888_Config, 640, 480);
bitmap.allocPixels();
if (NO_ERROR != initTexture(&texFrame, bitmap))
{
LOGD("GLTest: Unable to create a texture that is backed by SkBitmap");
return false;
}
SkCanvas canvas(bitmap);
SkPaint textAttribs;
textAttribs.setColor(0xFFFFFFFF);
textAttribs.setTextSize(SkIntToScalar(24));
const nsecs_t startTime = systemTime();
int frame_count = 0;
do
{
nsecs_t now = systemTime();
double time = now - startTime;
canvas.drawColor(0xFF0000FF);
canvas.drawText("Hello world", strlen("Hello world"), 200, 400,
textAttribs);
initTexture(&texFrame, bitmap); // Upload bitmap into canvas
glEnable (GL_BLEND);
EXPECT_NO_GL_ERROR(glBindTexture(GL_TEXTURE_2D, texFrame.id));
EXPECT_NO_GL_ERROR(glDrawTexiOES(0, 0, 0, texFrame.w, texFrame.h));
EGLBoolean res = eglSwapBuffers(mDisplay, mSurface);
if (res == EGL_FALSE)
break;
frame_count++;
if (0 == (frame_count % 150))
LOGD("GLTest: Completed %d frames", frame_count);
// 12fps: don't animate too fast to preserve CPU
const nsecs_t sleepTime = 83333 - ns2us(systemTime() - now);
if (sleepTime > 0)
usleep(sleepTime);
} while (!exitPending());
return false;
}
status_t GLTest::initTexture(Texture* texture, SkBitmap &bitmap)
{
bitmap.lockPixels();
const int w = bitmap.width();
const int h = bitmap.height();
const void* p = bitmap.getPixels();
GLint crop[4] =
{ 0, h, w, -h };
texture->w = w;
texture->h = h;
EXPECT_NO_GL_ERROR(glGenTextures(1, &(texture->id)));
EXPECT_NO_GL_ERROR(glBindTexture(GL_TEXTURE_2D, texture->id));
switch (bitmap.getConfig())
{
case SkBitmap::kA8_Config:
EXPECT_NO_GL_ERROR(
glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, w, h, 0, GL_ALPHA, GL_UNSIGNED_BYTE, p));
break;
case SkBitmap::kARGB_4444_Config:
EXPECT_NO_GL_ERROR(
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_SHORT_4_4_4_4, p));
break;
case SkBitmap::kARGB_8888_Config:
EXPECT_NO_GL_ERROR(
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, p));
break;
case SkBitmap::kRGB_565_Config:
EXPECT_NO_GL_ERROR(
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_RGB, GL_UNSIGNED_SHORT_5_6_5, p));
break;
default:
break;
}
EXPECT_NO_GL_ERROR(
glTexParameteriv(GL_TEXTURE_2D, GL_TEXTURE_CROP_RECT_OES, crop));
EXPECT_NO_GL_ERROR(
glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST));
EXPECT_NO_GL_ERROR(
glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST));
EXPECT_NO_GL_ERROR(
glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT));
EXPECT_NO_GL_ERROR(
glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT));
return NO_ERROR;
}
答案 0 :(得分：0)
我发现为什么我的代码不起作用。创建纹理时，宽度和高度必须是2的幂。例如，如果宽度为1920，则应创建宽度为2048的纹理（因为2048是下一个2次幂）。
将initTexture更改为以下。现在我可以将文本绘制到SkBitmap，然后将位图上传到纹理并绘制纹理。
下面是将给定位图上传到纹理的新initTexture。
bool initTexture(Texture* texture, const SkBitmap &bitmap)
{
bool result = true;
SkAutoLockPixels alp(bitmap);
const int w = bitmap.width();
const int h = bitmap.height();
const void* p = bitmap.getPixels();
int tw = 1 << (31 - __builtin_clz(w));
int th = 1 << (31 - __builtin_clz(h));
if (tw < w)
tw <<= 1;
if (th < h)
th <<= 1;
if (NULL == texture)
return false;
if (texture->id != 0)
{
glBindTexture(GL_TEXTURE_2D, texture->id);
switch (bitmap.getConfig())
{
case SkBitmap::kA8_Config:
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, w, h, GL_ALPHA, GL_UNSIGNED_BYTE, p);
break;
case SkBitmap::kARGB_4444_Config:
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, w, h, GL_RGBA, GL_UNSIGNED_SHORT_4_4_4_4, p);
break;
case SkBitmap::kARGB_8888_Config:
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, w, h, GL_RGBA, GL_UNSIGNED_BYTE, p);
break;
case SkBitmap::kRGB_565_Config:
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, w, h, GL_RGB, GL_UNSIGNED_SHORT_5_6_5, p);
break;
default:
break;
}
return true;
}
GLint crop[4] = { 0, h, w, -h };
texture->w = w;
texture->h = h;
glEnable (GL_TEXTURE_2D);
glGenTextures(1, &(texture->id));
glBindTexture(GL_TEXTURE_2D, texture->id);
switch (bitmap.getConfig())
{
case SkBitmap::kA8_Config:
glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, w, h, 0, GL_ALPHA, GL_UNSIGNED_BYTE, p);
break;
case SkBitmap::kARGB_4444_Config:
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_SHORT_4_4_4_4, p);
break;
case SkBitmap::kARGB_8888_Config:
if (tw != w || th != h)
{
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, tw, th, 0, GL_RGBA,
GL_UNSIGNED_BYTE, 0);
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, w, h, GL_RGBA,
GL_UNSIGNED_BYTE, p);
}
else
{
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, p);
}
break;
case SkBitmap::kRGB_565_Config:
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_RGB, GL_UNSIGNED_SHORT_5_6_5, p);
break;
default:
break;
}
glTexParameteriv(GL_TEXTURE_2D, GL_TEXTURE_CROP_RECT_OES, crop);
glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
return result;
}