Cita: imagettftexttransparent(resource im, int size, int angle, int x, int y, int col, string fontfile, string text, int pct)
imageTTFTextTransparent will draw transparent text on your image.
im is the image you want to edit.
size is the text size in points.
angle is the angle of the text.
x is the left coordinate of the text.
y is the top coordinate of the text.
fontfile is the font file you wish to use.
text is the text you wish to write.
pct is the percent that the text is transparent.
Según la documentación, $pct es el porcentaje de transparencia del texto.