diff options
| -rw-r--r-- | progs/demos/readpix.c | 60 |
1 files changed, 57 insertions, 3 deletions
diff --git a/progs/demos/readpix.c b/progs/demos/readpix.c index 2dc92f93fcd..c340e132bee 100644 --- a/progs/demos/readpix.c +++ b/progs/demos/readpix.c @@ -39,6 +39,10 @@ static GLenum ReadType = GL_UNSIGNED_BYTE; #endif #if 0 static GLenum ReadFormat = GL_RGB; +static GLenum ReadType = GL_UNSIGNED_BYTE; +#endif +#if 0 +static GLenum ReadFormat = GL_RGB; static GLenum ReadType = GL_UNSIGNED_SHORT_5_6_5; #endif #if 0 @@ -96,6 +100,45 @@ SetupPixelTransfer(GLboolean invert) } +/** + * Exercise Pixel Pack parameters by reading the image in four pieces. + */ +static void +ComplexReadPixels(GLint x, GLint y, GLsizei width, GLsizei height, + GLenum format, GLenum type, GLvoid *pixels) +{ + const GLsizei width0 = width / 2; + const GLsizei width1 = width - width0; + const GLsizei height0 = height / 2; + const GLsizei height1 = height - height0; + + glPixelStorei(GL_PACK_ROW_LENGTH, width); + + /* lower-left quadrant */ + glReadPixels(x, y, width0, height0, format, type, pixels); + + /* lower-right quadrant */ + glPixelStorei(GL_PACK_SKIP_PIXELS, width0); + glReadPixels(x + width0, y, width1, height0, format, type, pixels); + + /* upper-left quadrant */ + glPixelStorei(GL_PACK_SKIP_PIXELS, 0); + glPixelStorei(GL_PACK_SKIP_ROWS, height0); + glReadPixels(x, y + height0, width0, height1, format, type, pixels); + + /* upper-right quadrant */ + glPixelStorei(GL_PACK_SKIP_PIXELS, width0); + glPixelStorei(GL_PACK_SKIP_ROWS, height0); + glReadPixels(x + width0, y + height0, width1, height1, format, type, pixels); + + /* restore defaults */ + glPixelStorei(GL_PACK_SKIP_PIXELS, 0); + glPixelStorei(GL_PACK_SKIP_ROWS, 0); + glPixelStorei(GL_PACK_ROW_LENGTH, ImgWidth); +} + + + static void Display( void ) { @@ -111,8 +154,13 @@ Display( void ) glRasterPos2i(APosX, APosY); glEnable(GL_DITHER); SetupPixelTransfer(GL_FALSE); + glPixelStorei(GL_UNPACK_ALIGNMENT, 1); glDrawPixels(ImgWidth, ImgHeight, ImgFormat, GL_UNSIGNED_BYTE, Image); + /* might try alignment=4 here for testing */ + glPixelStorei(GL_UNPACK_ALIGNMENT, 1); + glPixelStorei(GL_PACK_ALIGNMENT, 1); + /* do readpixels, drawpixels */ glRasterPos2i(BPosX, 5); PrintString("Read/DrawPixels"); @@ -138,8 +186,14 @@ Display( void ) else { /* clear the temporary image to white (helpful for debugging */ memset(TempImage, 255, ImgWidth * ImgHeight * 4); +#if 0 + /* you might use this when debugging */ glReadPixels(APosX, APosY, ImgWidth, ImgHeight, ReadFormat, ReadType, TempImage); +#else + ComplexReadPixels(APosX, APosY, ImgWidth, ImgHeight, + ReadFormat, ReadType, TempImage); +#endif } glRasterPos2i(BPosX, BPosY); glDisable(GL_DITHER); @@ -253,14 +307,14 @@ Init( GLboolean ciMode ) printf("Loaded %d by %d image\n", ImgWidth, ImgHeight ); - glPixelStorei(GL_UNPACK_ALIGNMENT, 1); glPixelStorei(GL_UNPACK_ROW_LENGTH, ImgWidth); - glPixelStorei(GL_PACK_ALIGNMENT, 1); glPixelStorei(GL_PACK_ROW_LENGTH, ImgWidth); Reset(); - TempImage = (GLubyte *) malloc(ImgWidth * ImgHeight * 4 * sizeof(GLubyte)); + /* allocate an extra 1KB in case we're tinkering with pack alignment */ + TempImage = (GLubyte *) malloc(ImgWidth * ImgHeight * 4 * sizeof(GLubyte) + + 1000); assert(TempImage); } |