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vwebp: add checkboard background for alpha display

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Change-Id: Iefb02f38c0479e61334844d9110cd1b735f0395d
This commit is contained in:
James Zern 2012-07-09 23:01:52 -07:00
parent b35c07d9a7
commit a73b8978d1
1 changed files with 22 additions and 0 deletions
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22
examples/vwebp.c
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@ -112,6 +112,26 @@ static void PrintString(const char* const text) {
}
}
static void DrawCheckerBoard(void) {
const int square_size = 8; // must be a power of 2
int x, y;
GLint viewport[4]; // x, y, width, height
glPushMatrix();
glGetIntegerv(GL_VIEWPORT, viewport);
// shift to integer coordinates with (0,0) being top-left.
glOrtho(0, viewport[2], viewport[3], 0, -1, 1);
for (y = 0; y < viewport[3]; y += square_size) {
for (x = 0; x < viewport[2]; x += square_size) {
const GLubyte color = 128 + 64 * (!((x + y) & square_size));
glColor3ub(color, color, color);
glRecti(x, y, x + square_size, y + square_size);
}
}
glPopMatrix();
}
static void HandleDisplay(void) {
const WebPDecBuffer* pic = kParams.pic;
if (pic == NULL) return;
@ -121,6 +141,7 @@ static void HandleDisplay(void) {
glRasterPos2f(-1, 1);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glPixelStorei(GL_UNPACK_ROW_LENGTH, pic->u.RGBA.stride / 4);
DrawCheckerBoard();
glDrawPixels(pic->width, pic->height,
GL_RGBA, GL_UNSIGNED_BYTE,
(GLvoid*)pic->u.RGBA.rgba);
@ -136,6 +157,7 @@ static void HandleDisplay(void) {
glRasterPos2f(-0.95f, 0.80f);
PrintString(tmp);
}
glPopMatrix();
glFlush();
}