api: add OIIO_NODISCARD_ERROR to ImageOutput methods

- Annotate all ImageOutput write methods (write_image, write_scanline, write_scanlines, write_tile, write_tiles, write_rectangle, write_deep_scanlines, write_deep_tiles, write_deep_image), as well as open, close, and copy_image, with OIIO_NODISCARD_ERROR.
- Also fix the handful of internal callsites (imagebuf.cpp, maketexture.cpp, py_imagebuf.cpp) that were previously ignoring the return value of close(), either by propagating the error or by casting to void where the error path is already being handled.
- Assisted-by: Claude Sonnet 4.6

Signed-off-by: rose413 <116857309+rose413@users.noreply.github.com>

Author: rose413

src/iconvert/iconvert.cpp

@@ -494,7 +494,9 @@ convert_file(const std::string& in_filename, const std::string& out_filename)
         } while (ok && in->seek_subimage(subimage, miplevel));
     }
 
-    out->close();
+    if (!out->close()) {
+        errorfmt("Error closing \"{}\" : {}", out_filename, out->geterror());
+    }
     in->close();
 
     // Figure out a time for the input file -- either one supplied by

src/include/OpenImageIO/imageio.h

@@ -1811,7 +1811,10 @@ ImageBuf::write(string_view _filename, TypeDesc dtype, string_view _fileformat,
     }
     if (!write(out.get(), progress_callback, progress_callback_data))
         return false;
-    out->close();
+    if (!out->close()) {
+        error(out->geterror());
+        return false;
+    }
     if (progress_callback)
         progress_callback(progress_callback_data, 0);
     return true;

src/libOpenImageIO/imagebuf.cpp

@@ -1613,7 +1613,7 @@ test_demosaic_algo(const ImageBuf& src_image, const ImageBuf& mosaiced_image,
         std::string ext  = type.is_floating_point() ? "exr" : "png";
         std::string path = file_name + "_" + test_name + "." + ext;
         auto imageOutput = ImageOutput::create(ext);
-        imageOutput->open(path, demosaiced_image.spec());
+        (void)imageOutput->open(path, demosaiced_image.spec());
         demosaiced_image.write(imageOutput.get());
     }
 }
@@ -1650,7 +1650,7 @@ test_demosaic(const DemosaicTestConfig& config, const ImageBuf& src_image,
                 std::string path = file_name + "_src." + ext;
 
                 auto imageOutput = ImageOutput::create(ext);
-                imageOutput->open(path, mosaiced_image.spec());
+                (void)imageOutput->open(path, mosaiced_image.spec());
                 mosaiced_image.write(imageOutput.get());
             }
 
@@ -1741,7 +1741,7 @@ test_demosaic()
 
     if (write_files) {
         auto imageOutput = OIIO::ImageOutput::create("exr");
-        imageOutput->open("source.exr", src_image.spec());
+        (void)imageOutput->open("source.exr", src_image.spec());
         src_image.write(imageOutput.get());
     }
 

src/libOpenImageIO/imagebufalgo_test.cpp

@@ -187,7 +187,7 @@ time_write_image()
     OIIO_ASSERT(out);
     bool ok = out->open(output_filename, outspec);
     OIIO_ASSERT(ok);
-    out->write_image(bufspec.format, &buffer[0]);
+    (void)out->write_image(bufspec.format, &buffer[0]);
 }
 
 
@@ -203,7 +203,7 @@ time_write_scanline_at_a_time()
     size_t pixelsize         = outspec.nchannels * sizeof(float);
     imagesize_t scanlinesize = outspec.width * pixelsize;
     for (int y = 0; y < outspec.height; ++y) {
-        out->write_scanline(y + outspec.y, outspec.z, bufspec.format,
+        (void)out->write_scanline(y + outspec.y, outspec.z, bufspec.format,
                             &buffer[scanlinesize * y]);
     }
 }
@@ -221,7 +221,7 @@ time_write_64_scanlines_at_a_time()
     size_t pixelsize         = outspec.nchannels * sizeof(float);
     imagesize_t scanlinesize = outspec.width * pixelsize;
     for (int y = 0; y < outspec.height; y += 64) {
-        out->write_scanlines(y + outspec.y,
+        (void)out->write_scanlines(y + outspec.y,
                              std::min(y + outspec.y + 64,
                                       outspec.y + outspec.height),
                              outspec.z, bufspec.format,
@@ -245,10 +245,10 @@ time_write_tile_at_a_time()
     for (int z = 0; z < outspec.depth; z += outspec.tile_depth) {
         for (int y = 0; y < outspec.height; y += outspec.tile_height) {
             for (int x = 0; x < outspec.width; x += outspec.tile_width) {
-                out->write_tile(x + outspec.x, y + outspec.y, z + outspec.z,
-                                bufspec.format,
-                                &buffer[scanlinesize * y + pixelsize * x],
-                                pixelsize, scanlinesize, planesize);
+                (void)out->write_tile(x + outspec.x, y + outspec.y, z + outspec.z,
+                                       bufspec.format,
+                                       &buffer[scanlinesize * y + pixelsize * x],
+                                       pixelsize, scanlinesize, planesize);
             }
         }
     }
@@ -268,11 +268,11 @@ time_write_tiles_row_at_a_time()
     imagesize_t scanlinesize = outspec.width * pixelsize;
     for (int z = 0; z < outspec.depth; z += outspec.tile_depth) {
         for (int y = 0; y < outspec.height; y += outspec.tile_height) {
-            out->write_tiles(outspec.x, outspec.x + outspec.width,
-                             y + outspec.y, y + outspec.y + outspec.tile_height,
-                             z + outspec.z, z + outspec.z + outspec.tile_depth,
-                             bufspec.format, &buffer[scanlinesize * y],
-                             pixelsize /*xstride*/, scanlinesize /*ystride*/);
+            (void)out->write_tiles(outspec.x, outspec.x + outspec.width,
+                                   y + outspec.y, y + outspec.y + outspec.tile_height,
+                                   z + outspec.z, z + outspec.z + outspec.tile_depth,
+                                   bufspec.format, &buffer[scanlinesize * y],
+                                   pixelsize /*xstride*/, scanlinesize /*ystride*/);
         }
     }
 }

src/libOpenImageIO/imagespeed_test.cpp

@@ -792,7 +792,9 @@ write_mipmap(ImageBufAlgo::MakeTextureMode mode, std::shared_ptr<ImageBuf>& img,
         // ImageBuf::write transfers any errors from the ImageOutput to
         // the ImageBuf.
         errorfmt("Write failed: {}", img->geterror());
-        out->close();
+        if (!out->close()) {
+            errorfmt("Close failed: {}", out->geterror());
+        }
         return false;
     }
 
@@ -965,7 +967,9 @@ write_mipmap(ImageBufAlgo::MakeTextureMode mode, std::shared_ptr<ImageBuf>& img,
                 // ImageOutput to the ImageBuf.
                 errorfmt("Error writing \"{}\" : {}", outputfilename,
                          small->geterror());
-                out->close();
+                if (!out->close()) {
+                    errorfmt("Close failed: {}", out->geterror());
+                }
                 return false;
             }
             double wtime = writetimer();

src/libOpenImageIO/maketexture.cpp

@@ -273,7 +273,9 @@ ImageBuf_repr_png(const ImageBuf& self)
     if (!out || !out->open("temp.png", altered_spec))
         return py::bytes();
     self.write(out.get());
-    out->close();
+    if (!out->close()) {
+        return py::bytes();
+    }
 
     // Cast to const char* and return as python bytes
     const char* char_ptr = reinterpret_cast<const char*>(file_buffer.data());