fix encoding VAE tiling for Qwen Image (#1785)

Author: wbruna

otherarch/sdcpp/stable-diffusion.cpp

@@ -1553,10 +1553,19 @@ class StableDiffusionGGML {
         if (vae_tiling_params.enabled && !encode_video) {
             // TODO wan2.2 vae support?
             int C = sd_version_is_dit(version) ? 16 : 4;
-            if (!use_tiny_autoencoder) {
-                C *= 2;
+            int NE2, NE3;
+            if (sd_version_is_qwen_image(version)) {
+                NE2 = x->ne[3];
+                NE3 = C;
+            }
+            else {
+                if (!use_tiny_autoencoder) {
+                    C *= 2;
+                }
+                NE2 = C;
+                NE3 = x->ne[3];
             }
-            result = ggml_new_tensor_4d(work_ctx, GGML_TYPE_F32, W, H, C, x->ne[3]);
+            result = ggml_new_tensor_4d(work_ctx, GGML_TYPE_F32, W, H, NE2, NE3);
         }
 
         if (sd_version_is_qwen_image(version)) {