[Lang] Fix warning messages (taichi-dev#6716)

This PR fixes some warning messages in the official code. Also, forbid
committing `.ply` files generated by running the `diff_sph` example in
this repo.

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

.gitignore

@@ -89,3 +89,4 @@ imgui.ini
 .cache
 .do-not-clean
 *.dylib
+*.ply

python/taichi/_kernels.py

@@ -75,7 +75,7 @@ def vector_to_fast_image(img: template(), out: ndarray_type.ndarray()):
         r, g, b = 0, 0, 0
         color = img[i, img.shape[1] - 1 - j]
         if static(img.dtype in [f16, f32, f64]):
-            r, g, b = min(255, max(0, int(color * 255)))[:3]
+            r, g, b = ops.min(255, ops.max(0, int(color * 255)))[:3]
         else:
             static_assert(img.dtype == u8)
             r, g, b = color[:3]

python/taichi/examples/features/gui/gui_image_io.py

@@ -10,7 +10,7 @@
 @ti.kernel
 def paint():
     for I in ti.grouped(pixel):
-        pixel[I] = ti.random() * 255
+        pixel[I] = ti.u8(ti.random() * 255)
 
 
 paint()

python/taichi/ui/staging_buffer.py

@@ -1,4 +1,5 @@
 import numpy as np
+from taichi.lang import ops
 from taichi.lang._texture import Texture
 from taichi.lang.impl import ndarray
 from taichi.lang.kernel_impl import kernel
@@ -98,7 +99,7 @@ def copy_texture_to_rgba8(src: ti.types.texture(num_dimensions=2),
                           dst: ti.template(), w: ti.i32, h: ti.i32):
     for (i, j) in ti.ndrange(w, h):
         c = src.fetch(ti.Vector([i, j]), 0)
-        c = max(0.0, min(1.0, c))
+        c = ops.max(0.0, ops.min(1.0, c))
         c = c * 255
         px = ti.cast(c, u32)
         dst[i, j] = (px[0] << 0 | px[1] << 8 | px[2] << 16 | px[3] << 24)
@@ -113,7 +114,7 @@ def copy_image_f32_to_rgba8(src: ti.template(), dst: ti.template(),
         if ti.static(gray_scale):
             c = 0.0
             c = src[i, j]
-            c = max(0.0, min(1.0, c))
+            c = ops.max(0.0, ops.min(1.0, c))
             c = c * 255
             px[0] = px[1] = px[2] = ti.cast(c, u32)
         else:
@@ -125,7 +126,7 @@ def copy_image_f32_to_rgba8(src: ti.template(), dst: ti.template(),
                 else:
                     # 2D vector field source image
                     c = src[i, j][k]
-                c = max(0.0, min(1.0, c))
+                c = ops.max(0.0, ops.min(1.0, c))
                 c = c * 255
                 px[k] = ti.cast(c, u32)
         pack = (px[0] << 0 | px[1] << 8 | px[2] << 16 | px[3] << 24)
@@ -142,13 +143,13 @@ def copy_image_f32_to_rgba8_np(src: ti.types.ndarray(), dst: ti.template(),
         if ti.static(gray_scale):
             c = 0.0
             c = src[i, j]
-            c = max(0.0, min(1.0, c))
+            c = ops.max(0.0, ops.min(1.0, c))
             c = c * 255
             px[0] = px[1] = px[2] = ti.cast(c, u32)
         else:
             for k in ti.static(range(num_components)):
                 c = src[i, j, k]
-                c = max(0.0, min(1.0, c))
+                c = ops.max(0.0, ops.min(1.0, c))
                 c = c * 255
                 px[k] = ti.cast(c, u32)
         pack = (px[0] << 0 | px[1] << 8 | px[2] << 16 | px[3] << 24)