Generalizable image-based person re-identification (Re-ID) aims to recognize individuals across cameras in unseen domains without retraining. While visual features are sensitive to domain shifts, natural language descriptions remain consistent across domains, regardless of lighting changes and other biases. Since well-known multi-camera datasets lack textual descriptions, we update them with captions through a fine-tuned Vision-Language Model (VLM). We propose ReText, a novel method trained with textual supervision to enrich visual features with semantic cues. Besides, inspired by recent findings showing that incorporating single-camera data into training improves generalization, we also adopt this strategy. However, in contrast to such prior works, we exploit not only visual information but also the textual annotations naturally accompanying these samples. Finally, during training, ReText jointly optimizes three tasks: (1) Re-ID, (2) image-text matching, and (3) image reconstruction guided by text. Experiments demonstrate that ReText achieves strong generalization and significantly outperforms state-of-the-art methods on cross-domain Re-ID benchmarks. The expanded multi-camera datasets and VLM weights are publicly available at https://github.com/timmzak/ReText.
Figures & tables
Figure 1: Visual comparison of attention maps for models trained with and without textual supervision. The text-supervised model tends to focus on discriminative attributes like clothing and accessories instead of spreading attention over less informative areas. Attention maps are obtained from the last-layer [CLS]-to-patch attention, averaged across heads, and min-max normalized.
Figure 2: Overview of ReText. The model receives three types of inputs: (a) images from multi-camera, single-camera, or both data sources, (b) masked versions of images, and (c) textual captions. It jointly optimizes the Re-ID loss, the image-text matching loss, and the text-guided reconstruction loss.
Dataset
Multi
Text
#Images
#IDs
#Cams
CUHK03-NP
✓
✗
14,097
1,467
2
Market-1501
✓
✗
32,217
1,501
6
MSMT17
✓
✗
126,441
4,101
15
CUHK-SYSU
✓
✗
34,574
11,934
—
RandPerson
✓
✗
132,145
8,000
19
SYNTH-PEDES
✗
✓
4,791,771
312,321
—
Table 1: Statistics of datasets used in our experiments. The single-camera SYNTH-PEDES is significantly larger than all multi-camera datasets and textually annotated.
Figure 3: The block-structured similarity matrix. The caption embeddings are obtained from the text encoder trained within ReText on MSMT17 with textual supervision.
Table 2: Effect of single-camera data and textual supervision on cross-domain Re-ID. MSMT17 is used as multi-camera data for training.
Method
Tr. D.
CUHK03-NP
Market-1501
MSMT17
Average
Rank1
mAP
Rank1
mAP
Rank1
mAP
Rank1
mAP
TransMatcher [ 21 ]
Market-1501
22.2
21.4
—
—
47.3
18.4
34.8
19.9
QAConv-GS [ 22 ]
19.1
18.1
91.6
75.5
45.9
17.2
32.5
17.6
PAT [ 27 ]
25.4
26.0
92.4
81.5
42.8
18.2
34.1
22.1
LDU [ 30 ]
18.5
18.2
—
—
35.7
13.5
27.1
15.8
DCAC [ 14 ]
33.2
32.5
94.9
86.8
52.1
23.4
42.7
27.9
Table 3: Comparison of ReText with other state-of-the-art methods. Tr. D. denotes the training dataset. Metrics on the Market-1501 and MSMT17 datasets are excluded from average values in the first and second blocks, respectively.
Method
Market-1501
MSMT17
Average
Rank1
mAP
Rank1
mAP
Rank1
mAP
Image-Based Re-ID with Text Tokens
CLIP-ReID [ 18 ]
95.4
90.5
89.7
75.8
92.6
83.2
CLIP-DFGS [ 42 ]
93.7
85.5
86.4
66.3
90.1
75.9
Unified Re-ID Methods
PLIP [ 48 ]
97.3
93.2
—
—
—
—
Table 4: Comparison of ReText with other methods that support language supervision through text tokens or by unifying methods for image and text queries. STL and MTL versions of Instruct-ReID mean single-task and multi-task learning, respectively.
Table 8
Dataset
Texts
CUHK03-NP
Market-1501
Average
Rank1
mAP
Rank1
mAP
Rank1
mAP
MSMT17
32,621
61.9
61.8
93.3
81.4
77.6
71.6
SYNTH-PEDES
32,621
61.4
62.3
93.3
82.5
77.4
72.4
100,000
61.5
62.6
92.7
82.1
77.1
72.4
1,000,000
62.6
62.8
93.0
82.7
77.8
72.8
2,000,000
61.9
62.7
93.2
82.4
77.6
72.6
Table 7: Impact of increasing the quantity of single-camera data. The model is trained on MSMT17 as multi-camera data in both Mt (first row) and MSt (other rows) setups.
Configuration
Text
CUHK03-NP
Market-1501
Rank1
mAP
Rank1
mAP
in all Re-ID losses
✗
49.9
51.3
92.4
78.2
in all Re-ID losses
✓
63.4
62.9
93.3
82.8
in no Re-ID losses
✓
63.4
63.1
93.6
83.6
only in Lins
✓
63.1
62.9
93.6
83.6
only in Laug
✓
62.6
62.3
93.5
83.3
Table 8: Impact of using single-camera data in different Re-ID loss functions. The model is trained on MSMT17.
Loss
Ks
Rank1
mAP
CLIP loss
1
59.8
60.3
2
59.6
60.1
4
59.5
59.2
Soft CLIP loss
1
59.8
60.3
2
60.0
60.5
4
59.0
59.5
Table 9: Analysis of the number of same-identity instances ( Ks ) from single-camera data in a mini-batch for different image-text matching loss functions. The model is trained on MSMT17 and tested on CUHK03-NP.
Table 10: a) Analysis of the number of single-camera images in a mini-batch ( Ns ). b) Analysis of the α parameter in Eq. 5 for the Identity-aware Matching Loss. c) Analysis of the temperature parameter τ in Eq. 8 for the Structure-preserving Loss. The model is trained on MSMT17 and tested on CUHK03-NP.
Figure 4: Examples of image reconstruction in ReText. Each example shows the original image (left), masked input (middle), and the reconstructed output (right), alongside the corresponding caption. The model successfully recovers key visual details, highlighting the effectiveness of image-text training.
Method
M+MS+CS → C3
M+CS+C3 → MS
MS+CS+C3 → M
Average
Rank1
mAP
Rank1
mAP
Rank1
mAP
Rank1
mAP
Protocol 2
META [ 39 ]
35.1
36.3
49.9
22.5
86.1
67.5
57.0
42.1
ACL [ 41 ]
41.8
41.2
45.9
20.4
89.3
74.3
59.0
45.3
CLIP-ReID [ 18 ]
41.9
42.1
53.1
26.6
84.4
68.8
59.8
45.8
ReFID [ 29 ]
34.8
33.3
39.8
18.3
85.3
67.6
53.3
39.7
GMN [ 32 ]
42.1
43.2
50.9
24.4
87.1
72.3
60.0
46.6
Table 11: Comparison of ReText with other state-of-the-art methods according to Protocols 2 and 3. In this table, C3 is CUHK03-NP, MS is MSMT17, M is Market-1501, and CS is CUHK-SYSU. ReMix and DynaMix are excluded from this comparison because its authors did not evaluate the method using these protocols.
Method
Tr. D.
CUHK03-NP
Market-1501
Average
Rank1
mAP
Rank1
mAP
Rank1
mAP
QAConv [ 20 ]
MSMT17-merged
25.3
22.6
72.6
43.1
49.0
32.9
TransMatcher [ 21 ]
31.9
30.7
82.6
58.4
57.3
44.6
QAConv-GS [ 22 ]
27.6
28.0
82.4
56.9
55.0
42.5
PAT [ 27 ]
27.4
28.7
72.8
48.6
50.1
38.7
CLIP-DFGS [ 42 ]
37.1
25.7
80.9
55.2
59.0
40.5
Table 12: Comparison of ReText with other state-of-the-art methods according to Protocol 1 using the MSMT17-merged training dataset.
LLaVA
CUHK03-NP
Market-1501
Average
Rank1
mAP
Rank1
mAP
Rank1
mAP
HAM [ 12 ]
60.0
61.1
93.6
81.4
76.8
71.2
Ours (CIR)
59.7
60.7
93.5
81.4
76.6
71.1
Ours (UFine3C)
61.9
61.8
93.3
81.4
77.6
71.6
Ours (UFine3C † )
59.7
60.6
93.6
81.5
76.7
71.0
Table 13: Comparison of LLaVA models fine-tuned on different datasets. The CIR is the combination of CUHK-PEDES, ICFG-PEDES and RSTPReid datasets. UFine3C † denotes LLaVA fine-tuned on UFine3C, excluding images overlapping with the multi-camera datasets. The model is trained on MSMT17.
Dataset
#Texts
#Texts w. reps.
#Too Long Texts
CUHK03-NP
14,097
1
0
Market-1501
32,217
15
4
MSMT17
126,441
127
16
CUHK-SYSU
34,574
174
5
RandPerson
132,145
350
53
Table 14: Number of generated captions per dataset, and counts of captions containing repeated phrases (#Texts w. reps.) and exceeding the length threshold (#Too Long Texts).
Figure 5: Examples of defective generated captions. Hallucinated attributes that are not supported by the image are shown in red text, while repeated phrases produced by degenerate looping in the generation process are shown in gray text.
Figure 6: Qualitative examples of the attribute-matching categories from Figure 7 , showing manually annotated (M.A.) text, generated (Gen.) text, and their corresponding extracted attribute sets. The fields that differ between M.A. and Gen. texts are highlighted in red.
Figure 7: Attribute-level agreement between generated and human-annotated captions. Attributes were manually extracted from both captions and matched. Each chart displays the share of matches (correctly reproduced), extra attributes (noted in the generated text but omitted in the original), missing attributes (present in the original but omitted in the generated), and incorrect values (conflicting values).
Figure 8: High-frequency words of MSMT17 generated captions.
Figure 9: Examples of the textual descriptions generated by LLaVA for the images in the MSMT17 dataset.
Figure 10: Distribution of the word count in each generated caption for CUHK03, MSMT17, Market-1501, RandPerson, and CUHK-SYSU datasets. Min., max., avg. corresponds to the minimum, maximum, and average number of words.