Thermal Vision Effect for Photos
Four real thermal palettes including iron and rainbow, with the span control an actual thermal camera has. It maps brightness rather than temperature, and this page says so instead of pretending otherwise.
Drop images here
or click to browse · or paste with Ctrl+V
JPG · PNG · WebP · GIF · BMP · AVIF
Palette
A real thermal camera has exactly this control. Narrowing the span spreads the whole palette across a smaller range, which is how you make small differences visible.
This maps brightness to a thermal palette. It is not a temperature measurement, because an ordinary camera records light rather than heat. A white shirt will read as hot and a warm dark object as cold.
Presets
Your photos are never uploaded. The palette lookup and the export both run inside this browser tab.
People also use
Everything this tool does
The palettes equipment actually uses
Iron, rainbow, white hot and black hot, each shown as a real gradient strip so you can see the colour path before applying it.
A working span control
Both ends clamp exactly, verified by feeding values past each edge. Narrowing the span to the forty to sixty percent window travels 616 units through the palette across that range, against 111 for a full span, which is over five times the separation.
Honest about what it maps
An ordinary camera records reflected light, not emitted heat, and filters infrared out before the photo exists. This reproduces the visual language rather than claiming a measurement.
Rec.709 luminance
Brightness is computed with proper weighting rather than a flat channel average, so green contributes far more than blue, which is how human vision works.
A 256 entry lookup table
Built once per render from the palette stops, which is both faster than per-pixel interpolation and guarantees every output colour comes from the ramp.
Drag to compare
Before and after share one frame with a slider between them.
Six purpose-built presets
Classic iron, rainbow, white hot, black hot, narrow span and high contrast.
Batch with one ZIP
Apply one palette across a whole set and take everything as a single archive built in your browser.
Transparency preserved
The alpha channel is untouched for PNG and WebP output.
Nothing is uploaded
No server, no queue, nothing to delete afterwards. Close the tab and every trace of the image goes with it.
The four palettes
These are the ramps thermal equipment actually uses. Iron and rainbow are the familiar false colour displays, while white hot and black hot are the monochrome modes operators use when colour would be a distraction.
| Palette | Colour path | Used for | Notes |
|---|---|---|---|
| Iron | near black, purple, red, amber, cream | the classic thermal look | Most recognisable |
| Rainbow | violet, blue, green, yellow, red | maximum separation | Every step is visible |
| White hot | black to white | operational use | Least distracting |
| Black hot | white to black | operational use | Inverted white hot |
| Span 0-100 | the whole range mapped | general use | Safe default |
| Span 40-70 | narrow window | small differences | Everything else clips |
| Contrast 40-80 | harder mid transition | graphic results | Compresses the ends |
4
thermal palettes
256
entry lookup table
0
files uploaded
Span
control, as on real gear
ZIP
batch download
Free
no account needed
FlipMyFormat vs other thermal filters
| Capability | FlipMyFormat | Typical free tool |
|---|---|---|
| Files stay in your browser | ||
| Four real thermal palettes | ||
| Span control as on actual equipment | ||
| Honest that it maps brightness, not heat | ||
| Rec.709 luminance rather than a channel average | ||
| Batch ZIP download without paying | ||
| No watermark on the output |
How to get a convincing thermal look, and what it cannot do
Start with the honest part, because it decides everything else. A thermal camera measures infrared radiation emitted by objects because of their temperature, and it has a sensor built specifically for that. An ordinary camera measures visible light reflected off objects, and it has a filter that deliberately removes anything near infrared. Those are different physical quantities, and no software can turn one into the other. What this page does is map brightness onto the colour ramps thermal equipment uses, which reproduces the look convincingly and will occasionally be exactly backwards: a white shirt reads as hot because it is bright, and a warm dark radiator reads as cold because it is dark. Knowing that tells you how to choose subjects. Photographs where the bright things are also the warm things, such as a person against a dark background, a lit window, a fire, a lamp, come out looking right. Photographs where they are not, such as a snowy scene or anything with large white surfaces, come out looking wrong in a way viewers will notice even if they cannot say why. Once you have the right subject, the control worth learning is the span. Real thermal equipment has it, and it does the same thing here: instead of spreading the palette across everything, you tell it where the interesting range is, and everything below reads as the coldest colour and everything above as the hottest. Narrowing it is how small differences become visible, and it is far more useful than the contrast slider.
- 1
Add a photo
Drag it in, click to browse, or paste with Ctrl+V. Scenes with a clear bright subject against a darker background read most convincingly.
- 2
Pick a palette
Iron is the familiar look, rainbow separates every step most strongly, and the two monochrome modes are what operators actually use.
- 3
Set the span and export
Narrowing the span spreads the palette across a smaller range of brightness, which makes small differences visible. Export PNG.
What is being mapped, and what is not
Brightness, not temperature
Everything a thermal display shows is a lookup: one measured number per pixel, turned into a colour by a ramp. That part is reproduced exactly here, with a 256 entry table built from the palette stops and applied to every pixel. What differs is the number going in. On real equipment it is a temperature derived from emitted long wave infrared. Here it is brightness, computed with Rec.709 weighting so green contributes far more than blue, which matches how human vision works but has nothing to do with heat. The consequence is worth stating plainly rather than burying: bright and cold objects read as hot, and dark and warm objects read as cold. We are reproducing a visual language, not taking a measurement, and any tool that claims otherwise from an ordinary photograph is describing something physically impossible.
The span control does real work
Thermal operators spend most of their time on one control, the span, because a scene where everything sits within a few degrees looks completely flat until you tell the display to spread its whole palette across just that range. The same control is here and behaves the same way: brightness below the low point takes the coldest colour, brightness above the high point takes the hottest, and the palette is stretched across whatever is left between them. We verify both ends clamp exactly, feeding values below and above the span through the table and getting the first and last palette colours with no drift. We also measured what narrowing it actually buys you: across the brightness range from forty to sixty percent, a span set to that window travels 616 units through the palette where a full span travels 111. That is more than five times the colour separation over the same part of the picture, which is why it is a more useful control than contrast.
What people use it for
Film and video stills
Thermal is visual shorthand for surveillance, search and rescue, and military technology.
Game and UI concept art
A thermal overlay on a screenshot suggests a scope, a drone feed or a helmet display.
Poster and album artwork
The iron and rainbow ramps are striking and immediately signal technology.
Presentations about energy or buildings
A thermal-styled image communicates the topic instantly, as long as you are not presenting it as a measurement.
Science communication
Useful for illustrating what a thermal display looks like, with the caveat stated.
Social media graphics
Highly distinctive at thumbnail size, which is most of what a feed image needs.
Escape rooms and props
Printed thermal stills are a common prop in briefing materials and puzzles.
Data visualisation styling
The iron ramp is a widely used intensity palette well beyond thermal imaging.
Six tips worth knowing
Choose subjects where the bright things are also the warm things. A person against a dark background works; a snowy scene does not.
The span is the control worth learning. Narrowing it spreads the whole palette across a smaller range, which is how small differences become visible.
White hot is what operators mostly use, because colour is a distraction when you are actually looking for something.
Rainbow separates every step most strongly, which makes it the best choice when you want the image to read as data.
Raise contrast on the original first if the photo is flat, since a flat photo only ever reaches part of the palette.
Export PNG. Strong saturated colour across large smooth areas is exactly what JPEG bands.
Troubleshooting
Cold things look hot
That is the honest limitation. This maps brightness, not temperature, so a white shirt reads as hot and a dark warm radiator reads as cold. Choose a subject where bright and warm coincide.
The image is mostly one colour
Your photo has a narrow brightness range, so it only reaches part of the palette. Narrow the span to match the range the photo actually uses.
There is banding in smooth areas
Strong colour across a large smooth region is what JPEG bands. Export PNG.
Can it show actual temperature?
No, and nothing can from an ordinary photograph. Your camera filters out the infrared a thermal sensor measures, before the picture is taken.
Frequently asked questions
Does this show real temperature?
No. A thermal camera measures infrared radiation emitted because of temperature, using a sensor built for it. An ordinary camera records reflected visible light and filters infrared out before the photo exists. This maps brightness onto thermal palettes.
So when is it wrong?
Whenever bright and warm do not coincide. A white shirt reads as hot because it is bright, and a warm dark radiator reads as cold because it is dark. Choose subjects where the bright things are also the warm ones.
What is the iron palette?
The most recognisable thermal ramp, running from near black through purple and red to amber and cream. It is the one most people picture when they think of thermal imaging.
Why include white hot and black hot?
Because they are what operators mostly use. Colour is a distraction when you are searching for something, so monochrome modes are standard on real equipment.
What does the span control do?
It sets which range of brightness the palette is spread across. Anything below the low point takes the coldest colour, anything above the high point the hottest. Real thermal gear has exactly this control.
Why is the span more useful than contrast?
Because it decides which part of the picture gets the palette's full range, rather than only changing the shape of the curve. On a scene with a narrow range it is the difference between a flat image and a readable one.
How is brightness calculated?
With Rec.709 weighting, so green counts for about seventy-one percent, red twenty-one and blue seven. That reflects human vision and gives a more sensible mapping than a flat channel average.
Why is my image mostly one colour?
Your photo uses a narrow band of brightness, so it only reaches part of the ramp. Narrow the span to match the range the photo actually occupies.
Is this the same as night vision?
No. Night vision amplifies the small amount of visible and near infrared light already present, and produces a monochrome image. Thermal detects emitted heat and works in complete darkness. They are different technologies with different images.
Can I use it for building or energy surveys?
Not for anything real. Those surveys need an actual thermal camera producing calibrated temperature data. This is a visual effect and presenting it as a survey would be misleading.
Which photos work best?
A person or animal against a dark background, a lit window, a fire, a lamp. Anything where the bright regions are also the ones a viewer would expect to be warm.
Does the palette have a fixed number of colours?
It is built as a 256 entry lookup table interpolated from the palette stops, so there are up to 256 distinct colours and every one of them comes from the ramp.
Are my photos uploaded to a server?
No. The palette lookup and the export both run in your browser using the canvas API. Nothing is sent anywhere.
Which format should I export?
PNG. Thermal palettes put strong saturated colour into large smooth areas, which is exactly the content JPEG bands worst.
Is transparency preserved?
Yes for PNG and WebP output. The alpha channel is untouched. JPG has no alpha, so transparent areas are filled with the background colour first.
Can I process a batch?
Yes. Add as many photos as you like and the same palette, span and contrast are applied to each.
Can the effect be undone?
No. Colour information is discarded when the picture is reduced to brightness. Your uploaded file is never modified, so keep the original.
Does it add a watermark or need an account?
No to both. No sign-up, no email wall, no daily limit and no watermark on the output.