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authorBrian Paul <brian.paul@tungstengraphics.com>2005-05-18 15:44:13 +0000
committerBrian Paul <brian.paul@tungstengraphics.com>2005-05-18 15:44:13 +0000
commit8818eae253266b8e5df167ccd57567b36dbe32b6 (patch)
tree16fd1c5c6a2c06dfc8c2ce381408b8c5dcfa4cfb /progs/demos
parent2b2bd08589099cb480b983835b01cc76a766a3c4 (diff)
To better exercise pixel packing, replace regular glReadPixels with four
ReadPixels that get the image piece by piece.
Diffstat (limited to 'progs/demos')
-rw-r--r--progs/demos/readpix.c60
1 files changed, 57 insertions, 3 deletions
diff --git a/progs/demos/readpix.c b/progs/demos/readpix.c
index 2dc92f93fc..c340e132be 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);
}