--- title: Bounding boxes — FLUX 3 Image Klein | Runware Docs url: https://runware.ai/docs/models/bfl-flux-3-image-klein/guides/bounding-boxes description: "How to place, move and remove elements by region with FLUX 3 Image Klein: the 0 to 1000 grid, laying out a frame, reserving space for copy, and editing by box." --- ### [Introduction](https://runware.ai/docs/models/bfl-flux-3-image-klein/guides/bounding-boxes#introduction) A prompt can say "on the left" or "in the corner", but it **cannot say how far left or how large**. `settings.boundingBoxes` can. Each box **pins an element to a region of the frame**, and FLUX 3 Image Klein builds the rest of the scene around it. ![An overhead flat lay on gray concrete with a coral running shoe on the left, a black water bottle beside it, a smartwatch with a coral strap at the top right and an open white earbuds case at the bottom right](https://runware.ai/docs/assets/hero._YsFJqtv_Z1MFaxU.jpg) > **Prompt**: A flat overhead shot of running gear laid out on a smooth light gray concrete surface for a sports retailer banner: , , and , with clear empty concrete between them. Soft even daylight from above, small crisp shadows under each item. Photoreal flat lay product photography, 50mm lens, clean gray palette with bright accents. ```json [ { "id": "shoe_1", "targetBox": [120, 60, 880, 420], "description": "a coral and white running shoe lying on its side, toe pointing up" }, { "id": "bottle_1", "targetBox": [140, 480, 860, 610], "description": "a matte black insulated water bottle lying flat" }, { "id": "watch_1", "targetBox": [200, 690, 520, 890], "description": "a sports smartwatch with a coral silicone strap, the screen dark" }, { "id": "earbuds_1", "targetBox": [600, 700, 860, 880], "description": "an open white wireless earbuds charging case with both earbuds inside" } ] ``` Every item in the banner sits in the region its box gave it, with **even gaps between them** that a designer would otherwise have to arrange by hand. This guide covers how the coordinates work, how to lay out a frame from scratch, how to keep space free for copy, and how to move, remove and import elements in a reference. ### [How a box is written](https://runware.ai/docs/models/bfl-flux-3-image-klein/guides/bounding-boxes#how-a-box-is-written) A box is four numbers, `[top, left, bottom, right]`, on a **0 to 1000 grid whatever the output size**. `[0, 0, 1000, 1000]` is the whole frame and `[0, 500, 500, 1000]` is the top-right quarter. The same box lands in the same relative place on a square or a banner. Each box has an `id`, and the prompt mentions that id in angle brackets, ``, where the element belongs in the sentence. The `description` says **what the element is**, so the prompt can stay about the scene. **TypeScript**: ```typescript import { createClient } from '@runware/sdk' const client = await createClient({ apiKey: process.env.RUNWARE_API_KEY }) await client.connect() const [result] = await client.run({ model: 'bfl:flux@3-image-klein', positivePrompt: 'A flat overhead shot of running gear laid out on a smooth light gray concrete surface for a sports retailer banner: , , and , with clear empty concrete between them. Soft even daylight from above, small crisp shadows under each item. Photoreal flat lay product photography, 50mm lens, clean gray palette with bright accents.', width: 1536, height: 864, settings: { boundingBoxes: [ { id: 'shoe_1', targetBox: [ 120, 60, 880, 420 ], description: 'a coral and white running shoe lying on its side, toe pointing up' }, { id: 'bottle_1', targetBox: [ 140, 480, 860, 610 ], description: 'a matte black insulated water bottle lying flat' }, { id: 'watch_1', targetBox: [ 200, 690, 520, 890 ], description: 'a sports smartwatch with a coral silicone strap, the screen dark' }, { id: 'earbuds_1', targetBox: [ 600, 700, 860, 880 ], description: 'an open white wireless earbuds charging case with both earbuds inside' } ] } }) ``` **Python**: ```python import asyncio import os from runware import Runware async def main(): async with Runware(api_key=os.environ["RUNWARE_API_KEY"]) as client: results = await client.run({ "model": "bfl:flux@3-image-klein", "positivePrompt": "A flat overhead shot of running gear laid out on a smooth light gray concrete surface for a sports retailer banner: , , and , with clear empty concrete between them. Soft even daylight from above, small crisp shadows under each item. Photoreal flat lay product photography, 50mm lens, clean gray palette with bright accents.", "width": 1536, "height": 864, "settings": { "boundingBoxes": [ { "id": "shoe_1", "targetBox": [ 120, 60, 880, 420 ], "description": "a coral and white running shoe lying on its side, toe pointing up" }, { "id": "bottle_1", "targetBox": [ 140, 480, 860, 610 ], "description": "a matte black insulated water bottle lying flat" }, { "id": "watch_1", "targetBox": [ 200, 690, 520, 890 ], "description": "a sports smartwatch with a coral silicone strap, the screen dark" }, { "id": "earbuds_1", "targetBox": [ 600, 700, 860, 880 ], "description": "an open white wireless earbuds charging case with both earbuds inside" } ] } }) asyncio.run(main()) ``` **cURL**: ```bash curl https://api.runware.ai/v1 \ -H "Authorization: Bearer $RUNWARE_API_KEY" \ -H "Content-Type: application/json" \ -d '[ { "taskType": "imageInference", "taskUUID": "4f5a6b7c-8d9e-4f0a-b1c2-d3e4f5a6b7c8", "model": "bfl:flux@3-image-klein", "positivePrompt": "A flat overhead shot of running gear laid out on a smooth light gray concrete surface for a sports retailer banner: , , and , with clear empty concrete between them. Soft even daylight from above, small crisp shadows under each item. Photoreal flat lay product photography, 50mm lens, clean gray palette with bright accents.", "width": 1536, "height": 864, "settings": { "boundingBoxes": [ { "id": "shoe_1", "targetBox": [ 120, 60, 880, 420 ], "description": "a coral and white running shoe lying on its side, toe pointing up" }, { "id": "bottle_1", "targetBox": [ 140, 480, 860, 610 ], "description": "a matte black insulated water bottle lying flat" }, { "id": "watch_1", "targetBox": [ 200, 690, 520, 890 ], "description": "a sports smartwatch with a coral silicone strap, the screen dark" }, { "id": "earbuds_1", "targetBox": [ 600, 700, 860, 880 ], "description": "an open white wireless earbuds charging case with both earbuds inside" } ] } } ]' ``` **CLI**: ```bash runware run bfl:flux@3-image-klein \ positivePrompt="A flat overhead shot of running gear laid out on a smooth light gray concrete surface for a sports retailer banner: , , and , with clear empty concrete between them. Soft even daylight from above, small crisp shadows under each item. Photoreal flat lay product photography, 50mm lens, clean gray palette with bright accents." \ width=1536 \ height=864 \ settings.boundingBoxes.0.id=shoe_1 \ settings.boundingBoxes.0.targetBox.0=120 \ settings.boundingBoxes.0.targetBox.1=60 \ settings.boundingBoxes.0.targetBox.2=880 \ settings.boundingBoxes.0.targetBox.3=420 \ settings.boundingBoxes.0.description="a coral and white running shoe lying on its side, toe pointing up" \ settings.boundingBoxes.1.id=bottle_1 \ settings.boundingBoxes.1.targetBox.0=140 \ settings.boundingBoxes.1.targetBox.1=480 \ settings.boundingBoxes.1.targetBox.2=860 \ settings.boundingBoxes.1.targetBox.3=610 \ settings.boundingBoxes.1.description="a matte black insulated water bottle lying flat" \ settings.boundingBoxes.2.id=watch_1 \ settings.boundingBoxes.2.targetBox.0=200 \ settings.boundingBoxes.2.targetBox.1=690 \ settings.boundingBoxes.2.targetBox.2=520 \ settings.boundingBoxes.2.targetBox.3=890 \ settings.boundingBoxes.2.description="a sports smartwatch with a coral silicone strap, the screen dark" \ settings.boundingBoxes.3.id=earbuds_1 \ settings.boundingBoxes.3.targetBox.0=600 \ settings.boundingBoxes.3.targetBox.1=700 \ settings.boundingBoxes.3.targetBox.2=860 \ settings.boundingBoxes.3.targetBox.3=880 \ settings.boundingBoxes.3.description="an open white wireless earbuds charging case with both earbuds inside" ``` **JSON**: ```json { "taskType": "imageInference", "taskUUID": "4f5a6b7c-8d9e-4f0a-b1c2-d3e4f5a6b7c8", "model": "bfl:flux@3-image-klein", "positivePrompt": "A flat overhead shot of running gear laid out on a smooth light gray concrete surface for a sports retailer banner: , , and , with clear empty concrete between them. Soft even daylight from above, small crisp shadows under each item. Photoreal flat lay product photography, 50mm lens, clean gray palette with bright accents.", "width": 1536, "height": 864, "settings": { "boundingBoxes": [ { "id": "shoe_1", "targetBox": [ 120, 60, 880, 420 ], "description": "a coral and white running shoe lying on its side, toe pointing up" }, { "id": "bottle_1", "targetBox": [ 140, 480, 860, 610 ], "description": "a matte black insulated water bottle lying flat" }, { "id": "watch_1", "targetBox": [ 200, 690, 520, 890 ], "description": "a sports smartwatch with a coral silicone strap, the screen dark" }, { "id": "earbuds_1", "targetBox": [ 600, 700, 860, 880 ], "description": "an open white wireless earbuds charging case with both earbuds inside" } ] } } ``` Use ids that start with a letter and contain only letters, digits and underscores, like `shoe_1`, and keep each one unique within the request. **Boxes guide placement and size**, they are not masks: the element fills its region the way an object would, rather than to the pixel. ### [Laying out a frame](https://runware.ai/docs/models/bfl-flux-3-image-klein/guides/bounding-boxes#laying-out-a-frame) The two images below share a prompt and a seed. Only the box moved, from `[150, 80, 560, 360]` to `[150, 640, 560, 920]`, and **the vase moved with it**. ![A sage ceramic vase with white blossom branches standing at the left end of a walnut sideboard against a plaster wall](https://runware.ai/docs/assets/grid-left.DprcPdQh_myQXR.jpg) *targetBox \[150, 80, 560, 360\]* > **Prompt**: A straight-on shot at sideboard height: a low walnut sideboard against a warm white plaster wall, its top empty except for . Soft daylight from the left, a gentle shadow on the wall. Photoreal home decor photography, 35mm lens, warm neutral palette. ```json [ { "id": "vase_1", "targetBox": [150, 80, 560, 360], "description": "a tall matte sage ceramic vase holding a few branches of white blossom" } ] ``` ![The same sage vase with white blossom now standing at the right end of the walnut sideboard](https://runware.ai/docs/assets/grid-right.BZsQslUG_ZGTkHQ.jpg) *targetBox \[150, 640, 560, 920\]* > **Prompt**: A straight-on shot at sideboard height: a low walnut sideboard against a warm white plaster wall, its top empty except for . Soft daylight from the left, a gentle shadow on the wall. Photoreal home decor photography, 35mm lens, warm neutral palette. ```json [ { "id": "vase_1", "targetBox": [150, 640, 560, 920], "description": "a tall matte sage ceramic vase holding a few branches of white blossom" } ] ``` The box covers the vase and its branches together, so its top edge at 150 is where the blossom stops. **Size the box for the whole element**, including anything that rises above or spreads beside it. A box drawn around the vase alone would leave the branches to squeeze in or spill out. ### [Keeping space for copy](https://runware.ai/docs/models/bfl-flux-3-image-klein/guides/bounding-boxes#keeping-space-for-copy) Ads and banners need empty space for a headline, and an unboxed product tends to land in the middle of the frame. **One box on the product reserves the rest of the frame** without having to describe the empty part. ![White over-ear headphones with tan ear cushions standing in the center of a pale blue background](https://runware.ai/docs/assets/copy-unboxed.DWQAkWw5_Z6UqBU.jpg) *No box* > **Prompt**: An advertising image for wireless headphones on a seamless pale sky blue background: a pair of matte white over-ear headphones with tan leather ear cushions, standing upright and slightly turned toward the camera. Soft even studio light from the upper left, a gentle contact shadow on the floor. Photoreal product advertising photography, 85mm lens, airy pale blue and white palette. ![The same white headphones standing in the right third of the pale blue background, with the left half of the frame empty](https://runware.ai/docs/assets/copy-boxed.CdQKDvJr_Z2lvTte.jpg) *targetBox \[160, 600, 880, 920\]* > **Prompt**: An advertising image for wireless headphones on a seamless pale sky blue background: , standing upright and slightly turned toward the camera. Soft even studio light from the upper left, a gentle contact shadow on the floor. Photoreal product advertising photography, 85mm lens, airy pale blue and white palette. ```json [ { "id": "headphones_1", "targetBox": [160, 600, 880, 920], "description": "a pair of matte white over-ear headphones with tan leather ear cushions" } ] ``` With the box, the headphones sit in the right third and **the left half stays clean background**, ready for a headline and a button. The same approach works for a story with space at the top, or a thumbnail with a subject on one side. ### [Moving an element in a reference](https://runware.ai/docs/models/bfl-flux-3-image-klein/guides/bounding-boxes#moving-an-element-in-a-reference) With a reference in `inputs.referenceImages`, a box can point at something that is already in the photo. `referenceIndex` says **which reference the element comes from**, counting from 0, `sourceBox` says where it is now, and `targetBox` says where it should go. ![A hotel bedroom with a mustard velvet armchair on the left, a white bed with a gray throw in the center and a tall window with curtains on the right](https://runware.ai/docs/assets/source-bedroom.C0NiKjn-_CUUDb.jpg) *Source* > **Prompt**: A wide shot at standing height of a hotel bedroom corner: a white bed with a gray wool throw against the back wall in the center, on the left, and empty pale oak floor on the right in front of a tall window with sheer curtains. Soft daylight from the window, gentle shadows. Photoreal hospitality interior photography, 24mm lens, calm neutral palette. ![The same bedroom with the mustard armchair moved to the right in front of the window and empty floor on the left](https://runware.ai/docs/assets/edit-move.C-1bMycX_Z6QG0O.jpg) *Moved* > **Prompt**: Move to the right side of the room in front of the window, angled toward the bed, and leave empty pale oak floor where it stood. Keep the bed, the throw, the window, the curtains, the light and the framing unchanged. ```json [ { "id": "armchair_1", "referenceIndex": 0, "sourceBox": [420, 60, 900, 360], "targetBox": [420, 640, 900, 940], "description": "the mustard yellow velvet armchair" } ] ``` **TypeScript**: ```typescript import { createClient } from '@runware/sdk' const client = await createClient({ apiKey: process.env.RUNWARE_API_KEY }) await client.connect() const [result] = await client.run({ model: 'bfl:flux@3-image-klein', positivePrompt: 'Move to the right side of the room in front of the window, angled toward the bed, and leave empty pale oak floor where it stood. Keep the bed, the throw, the window, the curtains, the light and the framing unchanged.', inputs: { referenceImages: [ 'https://im.runware.ai/image/os/a14d18/ws/2/ii/d0ba0393-8017-45eb-bb14-d8ece004a1fe.jpg' ] }, settings: { boundingBoxes: [ { id: 'armchair_1', referenceIndex: 0, sourceBox: [ 420, 60, 900, 360 ], targetBox: [ 420, 640, 900, 940 ], description: 'the mustard yellow velvet armchair' } ] } }) ``` **Python**: ```python import asyncio import os from runware import Runware async def main(): async with Runware(api_key=os.environ["RUNWARE_API_KEY"]) as client: results = await client.run({ "model": "bfl:flux@3-image-klein", "positivePrompt": "Move to the right side of the room in front of the window, angled toward the bed, and leave empty pale oak floor where it stood. Keep the bed, the throw, the window, the curtains, the light and the framing unchanged.", "inputs": { "referenceImages": [ "https://im.runware.ai/image/os/a14d18/ws/2/ii/d0ba0393-8017-45eb-bb14-d8ece004a1fe.jpg" ] }, "settings": { "boundingBoxes": [ { "id": "armchair_1", "referenceIndex": 0, "sourceBox": [ 420, 60, 900, 360 ], "targetBox": [ 420, 640, 900, 940 ], "description": "the mustard yellow velvet armchair" } ] } }) asyncio.run(main()) ``` **cURL**: ```bash curl https://api.runware.ai/v1 \ -H "Authorization: Bearer $RUNWARE_API_KEY" \ -H "Content-Type: application/json" \ -d '[ { "taskType": "imageInference", "taskUUID": "1a2b3c4d-5e6f-4a7b-8c9d-0e1f2a3b4c5d", "model": "bfl:flux@3-image-klein", "positivePrompt": "Move to the right side of the room in front of the window, angled toward the bed, and leave empty pale oak floor where it stood. Keep the bed, the throw, the window, the curtains, the light and the framing unchanged.", "inputs": { "referenceImages": [ "https://im.runware.ai/image/os/a14d18/ws/2/ii/d0ba0393-8017-45eb-bb14-d8ece004a1fe.jpg" ] }, "settings": { "boundingBoxes": [ { "id": "armchair_1", "referenceIndex": 0, "sourceBox": [ 420, 60, 900, 360 ], "targetBox": [ 420, 640, 900, 940 ], "description": "the mustard yellow velvet armchair" } ] } } ]' ``` **CLI**: ```bash runware run bfl:flux@3-image-klein \ positivePrompt="Move to the right side of the room in front of the window, angled toward the bed, and leave empty pale oak floor where it stood. Keep the bed, the throw, the window, the curtains, the light and the framing unchanged." \ inputs.referenceImages.0=https://im.runware.ai/image/os/a14d18/ws/2/ii/d0ba0393-8017-45eb-bb14-d8ece004a1fe.jpg \ settings.boundingBoxes.0.id=armchair_1 \ settings.boundingBoxes.0.referenceIndex=0 \ settings.boundingBoxes.0.sourceBox.0=420 \ settings.boundingBoxes.0.sourceBox.1=60 \ settings.boundingBoxes.0.sourceBox.2=900 \ settings.boundingBoxes.0.sourceBox.3=360 \ settings.boundingBoxes.0.targetBox.0=420 \ settings.boundingBoxes.0.targetBox.1=640 \ settings.boundingBoxes.0.targetBox.2=900 \ settings.boundingBoxes.0.targetBox.3=940 \ settings.boundingBoxes.0.description="the mustard yellow velvet armchair" ``` **JSON**: ```json { "taskType": "imageInference", "taskUUID": "1a2b3c4d-5e6f-4a7b-8c9d-0e1f2a3b4c5d", "model": "bfl:flux@3-image-klein", "positivePrompt": "Move to the right side of the room in front of the window, angled toward the bed, and leave empty pale oak floor where it stood. Keep the bed, the throw, the window, the curtains, the light and the framing unchanged.", "inputs": { "referenceImages": [ "https://im.runware.ai/image/os/a14d18/ws/2/ii/d0ba0393-8017-45eb-bb14-d8ece004a1fe.jpg" ] }, "settings": { "boundingBoxes": [ { "id": "armchair_1", "referenceIndex": 0, "sourceBox": [ 420, 60, 900, 360 ], "targetBox": [ 420, 640, 900, 940 ], "description": "the mustard yellow velvet armchair" } ] } } ``` The armchair arrives in its new place with the same velvet and walnut legs, and the floor where it stood is clear. **A target box of a different size resizes** the element as it moves, and a target equal to the source keeps it in place, which is how you edit one object without touching its position. > [!NOTE] > `referenceIndex` and `sourceBox` only apply when the request carries reference images. Without references, every box needs a `targetBox`, and the request is a layout from scratch. ### [Removing an element](https://runware.ai/docs/models/bfl-flux-3-image-klein/guides/bounding-boxes#removing-an-element) Set `targetBox` to `null` and the element has nowhere to go, so **the box removes it**. Say in the prompt what should continue across the gap. **Source**: ![A white quartz kitchen counter against white subway tiles with a chrome toaster on the left, a bowl of lemons in the center and a jar of wooden spoons on the right](https://runware.ai/docs/assets/source-counter.BTeD2cSp_1373Pe.jpg) > **Prompt**: A straight-on shot at counter height of a white quartz kitchen counter against a wall of glossy white subway tiles: on the left, a wooden bowl of lemons in the center and a ceramic jar of wooden spoons on the right. Soft morning daylight from the right. Photoreal real estate kitchen photography, 35mm lens, bright white palette. **Removed**: ![The same counter with the toaster gone and clean quartz and tiles where it stood, the lemons and spoons unchanged](https://runware.ai/docs/assets/edit-remove.BXBoXLXN_Z2lI0Fk.jpg) > **Prompt**: Remove and continue the clean white quartz counter and the subway tiles where it stood. Keep the bowl of lemons, the jar of spoons, the light and the framing unchanged. The tile courses continue through the space the toaster covered, and the bowl and jar have not shifted. This is the cleanup pass on a **real estate photo before it goes on the listing**: small appliances and clutter out, everything else as photographed. ### [Bringing in an element from another image](https://runware.ai/docs/models/bfl-flux-3-image-klein/guides/bounding-boxes#bringing-in-an-element-from-another-image) `referenceIndex` can point at a reference other than the scene. Send the product and the room, say which image is the scene, and **box the product in its packshot and in the room**. ![The bent oak lounge chair with cream boucle cushions standing on a jute rug in a hotel reading room with an arched window and tall bookshelves](https://runware.ai/docs/assets/edit-place.acihjfl2_ZR7T7l.jpg) > **Prompt**: Use image 2 as the scene, keeping the arched window, the bookshelf, the jute rug, the terrazzo floor and the warm afternoon light unchanged. Place on the rug in the center of the room, angled slightly toward the window, with a soft shadow on the rug that matches the window light. Keep the chair exact, including its curved oak frame and its cream boucle cushions. **Image 1, the chair**: ![A lounge chair with a curved oak frame and cream boucle cushions on a white background](https://runware.ai/docs/assets/ref-chair.mJFVRJSD_v6RXd.jpg) > **Prompt**: A furniture packshot on a seamless white background: , seen in three-quarter view. Even soft studio light, a faint contact shadow. Photoreal furniture e-commerce packshot, clean white palette. ```json [ { "id": "chair_1", "referenceIndex": 0, "sourceBox": [80, 250, 960, 750], "targetBox": [330, 360, 930, 660], "description": "the lounge chair with the curved oak frame and cream boucle cushions" } ] ``` **Image 2, the scene**: ![A hotel reading room with an arched window, tall built-in bookshelves and an empty jute rug on a terrazzo floor](https://runware.ai/docs/assets/ref-room.PGLsCfAB_Z2lrDAI.jpg) > **Prompt**: A wide shot at standing height of a quiet reading corner in a boutique hotel lounge: a tall arched window on the left, a low built-in bookshelf along the back wall and a jute rug on a terrazzo floor, with empty floor on the rug in the center of the frame. Warm afternoon daylight from the window. Photoreal hospitality interior photography, 24mm lens, warm sand and cream palette. The chair comes from image 1, so its box has `referenceIndex: 0` and a `sourceBox` around the chair in the packshot. Its `targetBox`, `[330, 360, 930, 660]`, puts it on the rug at **the size a real chair would have** at that distance from the camera. The room and its window light are unchanged. ### [Tips for best results](https://runware.ai/docs/models/bfl-flux-3-image-klein/guides/bounding-boxes#tips-for-best-results) 1. **Put the top coordinate first.** A box is `[top, left, bottom, right]`, and a swapped pair puts the element in the wrong place. 2. **Mention every box in the prompt.** Each `id` should appear as `` where the element belongs in the sentence. 3. **Size the box for the whole element.** Leave room for branches, handles, straps and shadows, or the element gets squeezed. 4. **Use one box to reserve empty space.** Boxing only the product keeps the rest of the frame free for copy. 5. **Say what fills the gap.** When an element moves or is removed, name the surface that should continue where it was. 6. **Match the target size to the scene.** A product placed into a room needs a box the size it would really be at that spot, or it reads as a sticker.