Image Convert Ninja

Mar 17, 2023 Update
Open Image using button below
Open Image using button below
Drag and Drop image file right here
Tone Mapping Exposure
<= darker | brighter =>
Compression / Quality (%)
<= lower size | better quality =>

How to Use

Get Started

All you need to do is provide an image to Image Convert Ninja. Below described several ways to do this.

After adding an image to Image Convert Ninja, it will load image into memory and displays it directly in the Image Viewer.

If you finish using current image and want to open another, there is no need to reload this page. Just add another image as before, and image viewer will show you newly added image instead. You can change images as many times as you want.

Viewport Controls

Image Viewer is an interactive area at the top of the page where you can literally view and manipulate by currently opened image.

The great thing about Image Viewer is that it's not an average statically embedded image on a page, but a fully interactive image viewer. If you've ever used any type of desktop 2D editor, like Photoshop, you already know what it is. If you haven't, just play with it and you will instantly understand what it is about.


To panning / moving image in any direction inside Image Viewer, simply click anywhere in the Image Viewer, hold down left mouse button and move cursor. That is, drag an image in any direction and it will follow your moves. When you done positioning image as you like, just release mouse button.


To zoom in / out, hover cursor over any part of the Image Viewer and scroll mouse wheel. It will move image to or from you, depending on scrolling direction.

Fitting Image to Viewport

When panning and zooming, you may want to reset Image Viewer to default view. Not a problem at all, just look at the right bottom corner of the Image Viewer and you'll find Fit Image to Viewport button there. Once you click it, your image will automatically fit to the current Image Viewer size. It's also a good way to adjust an image to the new Image Viewer size when you go full screen.

Going Full Screen

If you want to see your image on largest possible area of the screen, then you need to enter full screen mode. Corresponding, button is located in upper right corner of the Image Viewer and it called Full Screen.

In full screen mode, Image Viewer's background turns black to help you focus on actual image rather than bright white background.

To exit full screen mode, use Fit Image to Viewport button again or just press "Esc" key on keyboard.

Another thing to know about full screen mode is that switching to full screen will not resize an image on a screen, it will literally expand only the Image Viewer area. Therefore, when you switch to full screen and back, an image size remains the same.

Input Formats

Although this tool is called Image Convert Ninja, HDR processing is the feature, but not a limitation on input formats. This meant, you can use any supported image (see below) as input. It doesn't have to be HDR images only, you can also view, edit and convert regular LDR pictures as well.

LDR Formats (8-bit and 16-bit)

Image Convert Ninja supports images of most common formats, namely: JPEG, PNG, BMP, WEBP, AVIF, SVG, GIF*, APNG* and TIFF**.

* GIF and APNG images will always display only a first frame, but will not play animation.

** You can open 8-bit and 16-bit TIFF files with LZW, ZIP & JPEG image compression. 32-bit TIFF files are not currently supported.

HDR Formats (32-bit)

There are several formats that can contain 32-bit data per pixel or more, but the most popular are Radiance RGBE and OpenEXR. Both are supported by this Image Convert Ninja. This meant that you can open HDR image files with following extensions: HDR and EXR.

Exceptions of OpenEXR

HDR is a single-page (no image layers support), very straightforward format. So far, we do not encounter with HDR files that cannot be opened by Image Convert Ninja.

EXR format, on the other hand, is a very cool but very complex multi-page format. It supports layers, including cryptomatte layers, transparency (alpha channel), multiple image compression algorithms, different color depths and more.

Various programs that can store images in OpenEXR use different configurations and versions of it. Some EXR files cannot be opened even with powerful desktop 2D editors due to this complexity and variety.

If you can't open some EXE file with this online app, either particular image resolution is too high for your browser to handle, or you've encountered an uncommon EXR implementation just described above.

For more technical information about this app and any other troubleshooting, see Tech Spec section below.

Tone Mapping Exposure Control

HDRI Exposure

For HDR images, Tone Mapping Exposure control tool lets you choose which part of entire high dynamic range you will see through limited low dynamic range of your screen.

Move slider to the left to look at darker, less exposed side, or move slider to the right to see color information closer to more light exposed values of entire high dynamic range. In addition, there is a spinner, with which you can not only see current value of Exposure, but also directly change this value with precision of 0.01, including going beyond upper limit of the slider to an Exposure value up to 10.

In turn, Exposure value is a key value of Tone Mapping algorithm, which is an algorithm that actually converts (filters or squeeze) high dynamic values into low dynamic ones. That's why this post-processing feature of Image Convert Ninja is called not just Exposure, but Tone Mapping Exposure.

Currently, classic Linear Tone Mapping algorithm is used, which is also used in most 2d editors. It creates high-contrast images at low and medium exposure, but produce excessive overburn when do filtering of high-exposure values.

LDRI Exposure

For LDR images, Tone Mapping Exposure correction can also be applied, but because LDR images do not contain any additional information other than currently visible, ability to correct, or, better said, shift exposure in LDR images is very limited.

Moving slider to the left will only make overall look of an image darker, with no extra details revealed in a bright areas. White colors will turn gray and that's it. As well as moving slider to the right will only make overall look of an image brighter, without showing any additional details, in dark areas. Because LDR image is clamped by low bit rate and there are no (or almost no for 16-bit images) hidden details outside what is currently visible by your 8-bit display-device.

Default Exposure

Default exposure value is 1. It shows an image with the same look it had when it was created. A value of 1 means no exposure correction applied.

When you change it to any other value that is appropriate for your current image, program remembers that value and applies it to any other subsequent images that you open after. That is, when you open another image, program does not automatically reset current exposure value to default one. This is done intentionally so that you can apply the same exposure correction to all next images you work on during current session (until you close this page).

If you want to reset current exposure value to default value, you can either explicitly set it to 1 or simply press reset button located in the upper right corner of Tone Mapping Exposure control tool.

Free Online Image Converter | Сompressor | Optimizer

When you have finished adjusting exposure of your 32-bit HDR image or leave as is, next step will be is to save it as an 8-bit LDR image. And that's exactly what Converter Panel does. It allows you to select any format from the list of options, adjust its compression (if it is supported) and save it for future use as a common 8-bit image.

You can also do the same for any supported LDR image. This means that you can not only convert HDR images to LDR, but also convert one LDR format to another. For example, you can convert PNG to JPEG with custom level of compression. So this panel allows you to use application not only as image viewer, but as online image format converter.

Any exposure adjustments will be applied when saving image, so saved / converted image will look exactly as you see it in a Image Viewer of Image Convert Ninja.

Saving Images

To save image locally on your device, select desired format using Format Drop-Down List at the right bottom of Converter Panel and press Save Image button.

Converter will prepare image in chosen format for you and allow you to save it. Image preparation process can take from milliseconds to several seconds, depending on actual image resolution and performance of your device.

After preparation is done, on desktop computer, browser will open standard "Save As" dialog, where you can choose where you want to save your image on a local drive. On a mobile device, browser will automatically save image to default "Downloads" folder.

Compressible Formats

Compressible format allows you to change a level of its compression manually, while maintaining the same resolution with a smaller file size, but at the same time reducing image details and visual quality. This type of compression is also called Lossy Compression.

You can control compression level manually using slider or spinner on Converter Panel.

These are: JPEG and WEBP.

If JPEG does not require special presentation, WEBP, on the other hand, although not invented today, is still considered a new and modern standard for web imaging. Despite its web-oriented nature, today WEBP is even supported by some desktop image viewers. It has better compression compared to JPEG, so this is a very good option when you need to save really small lossy compression images for any use.

One more thing to keep in mind. If you save an image with a compression / quality level other than 100%, a postfix with corresponding number will be added to the name of saved file in order to indicate that image has been compressed to specified level. For example, suggested name for "my-picture" image, saved with 85% quality JPEG, would be "my-picture_(85).jpg". And so on.

Basename for saved file is always taken from a name of input image file that you provide.

Lossless Formats

Lossless formats does not provide manual adjustment of compression level, as it either does not support compression or it is already compressed without compromising visual quality of an image. That is, lossless format are not compressible manually and transmit 100% original image details without losses in quality.

If you choose to save image in Lossless format, compression level controls will be locked.

These are: PNG, AVIF, GIF, BMP, ICO.

AVIF, like WEBP, is another web format that can perform both lossless and lossy compression. In lossless compression, it is even better than WEBP. However, it is newer than WEBP and still has less support, including among web browsers. Currently, Image Convert Ninja relies directly on browsers API (Web API), and not yet support manual compression for this format, so for now it titled as lossless.

ICO, also web-format related to creation of favicon.ico and is mainly used by web developers. If you're not a webmaster or web developer, most likely you don't need it, so just ignore this format and use familiar image formats only.

Base64 Image

These online image converter not only allows you to save image as a file of selected format, but also allows you to copy this image, in selected format, to clipboard as Base64 encoded string.

To get Base64 encoded image of desired format, use Format Drop-Down List and select appropriate one. If it is Compressible format, you can set appropriate compression level. Then click button located at lower left corner of Converter Panel. Program will automatically prepare and copy to clipboard image in selected format as a Base64 encoded string. Now you can paste Base64 image from clipboard wherever you need.

As with ICO, Base64 images are also a very specific format for web development. In short, it's a way to embed an image directly into page's HTML code, instead of fetching it as a separate file from a server using separate request. Base64 images can be useful for representing small tillable images that, for instance, serves as background.

For example, when you first open this page, Image Viewer's background, that looks like a gray wired various size honeycombs on a white backdrop, is actually a Base64 encoded image embedded directly into corresponding CSS selector. It looks as following.

background: url( Base64 image string goes here... )

As mentioned above for ICO, Base64 is also a very web-related data format. If you're a web developer or website layout designer, you probably already know what it is and why you need it. If you are not, most likely you don't need this highly specialized feature at all. Therefore, skip this feature for now until you really need it.


When browser loads this page, it also loads all relevant resources, including Image Convert Ninja software, which immediately starts working in browser as long as this page remains open. This software runs in a browser's Runtime Environment and uses its built-in functionality. That is, it works directly in your web browser as a completely local application. Despite you need an Internet connection to initially load this page, Image Convert Ninja itself is technically an offline or Client-Side application. When you have it in your browser, it will continue to work even if you lose your Internet connection. Image Convert Ninja process images, including image conversion stage, by computing power of your device, so nothing is sent to our server. All images you use remain confidential.

Tech Specs

Image Convert Ninja application uses WebGL under the hood. See About section for more details. This means that in order to use it, you need to have a browser with full WebGL support and appropriate graphics hardware. You can check if your browser supports WebGL here: Get.WebGL.Org or here: Detect WebGL.

Most modern browsers support WebGL. So, if you use Firefox 23+, Chrome 24+, Safari 8+, Internet Explorer 11+ or Edge, everything should work as expected.

Image Convert Ninja application has been tested on latest versions of Chrome, Firefox and Edge in Windows 10, and it works in them properly.

This program is mobile friendly and quite convenient to use on mobile devices. You can view, edit and convert formats online with this application directly with your mobile phone or tablet as efficiently as on a desktop computer.

Image Convert Ninja is a client-side web application that directly depends on a features available in your browser. This means that it is capable of what your browser allows and helps with, but at the same time it is limited by what browser does not support or restrict. Some restrictions are set by browser developers on purpose, to protect browser users and ensure optimal page rendering performance. For example, browsers set limits on maximum image size / resolution that can be manipulated in the browser, even if your hardware can handle a much larger image. Such restrictions are hard-coded in your browser (or set by appropriate flags in browser settings) and cannot be overwritten from within web application itself.

Maximum Input Resolution (Chromium)

Although image viewer Image Viewer looks as flat 2D entity, technically it is a full fledged 3D application and it relies on so called Max Texture Size property of WebGL render engine. This property determines maximum image resolution that currently can be seen in the Image Viewer.

Max Texture Size vary depending on your browser and GPU. For desktop computers it is limited to about 16K (16384*16384 px) resolution. For mobile devices, this property value will be lower.

If you are interested in exact value for your configuration, visit WebGL Report web-site. You will find value of Max Texture Size for you device, in the "Textures" zone.

If you open images with a resolution lower than Max Texture Size, Image Viewer will display them as is. If you provide an image with a resolution higher than Max Texture Size, this program will load it and automatically resize it, while maintaining original image aspect ratio, so a larger image side will be equal to Max Texture Size.

This meant, that even if you provide, say, a 20K image, it will be internally resized, and then in Image Viewer it will be displayed as 16K.

Although, you can use larger images, your browser considers certain resolutions to be "too large" and will not allow you to upload a very large images. For desktops, it is about resolution of 32K.

The good news is that 16K is more than enough for most uses.

Maximum Input Resolution (Firefox)

Latest versions of Firefox with their Image API refuses to process images larger than 8K (8192*8192 px) despite of Max Texture Size value.

The good news is, that 8K is still a good resolution for most of cases and, of course, you can use less restrictive Chromium-based browser of your choice. Fortunately, there are a lot of them now.

Maximum Output Resolution

Output image resolution currently determined and limited by size of so called Drawing Buffer. It literally determines a largest image that can be rendered on the browser canvas. For desktops, it is limited to about 8K resolution. For mobile devices, this property value will be lower.

If you open an image with a resolution greater than Drawing Buffer of your browser and then save it, then resolution of saved image will be limited to the size of the Drawing Buffer while maintaining aspect ratio from original image.

If you open an image with a resolution higher than maximum Drawing Buffer size of your browser and then save it, the resolution of saved image will be limited by maximum Drawing Buffer size, while maintaining aspect ratio of original image.

For example, your browser's Drawing Buffer has a resolution of 8K, and you open 16K HDR image. Then you save it, say, in PNG format. Saved PNG file will have a resolution of 8K instead of 16K.

This is a noticeable limitation, but we are working on how to save images with a resolution not lower than resolution of input image.

You can read more about planed updates in Improvements Roadmap section.


As mentioned, Image Convert Ninja is a client-side (in-browser) program that performs all image processing using only computing power of your device. Both CPU and GPU are used. Therefore, speed of loading, converting and saving images depends on performance of your equipment and the size of images itself.

If you open a very large image of several hundred megabytes, this program will handle it, but it will take a few seconds to accomplish.

It may happen that your browser decides that this program performed abnormally long, becoming uncontrolled and unresponsive. Then it will give you a small pop-up window that says something like "Page Unresponsive" and suggest to "Wait" or "Exit" the page. In this case, you do not need to do anything, just wait until image loading is complete. Browser will then close that pop-up automatically.

Raster Oriented Image Processing

Online HDRI Image Viewer is a raster images processing tool. When you open any supported image, including SVG, this program first rasterize it. Then, when you save it or copy as Base64 string, Online HDRI Image Viewer will save it not as set of a vector shapes, but as a bitmap image.


Transparency for output images is not currently supported. Any transparent part will be filled with black.

Roadmap for Improvements

Following is a list of planned improvements to this online program. It does not define order or deadlines, but it is what we plan to improve in near future. If you have additional suggestions on what improvements you want to see here, please tell us about.

  • Manual compression support for some of formats currently listed as Lossless.

  • Comparison of lossless image with it compressed version, during real-time tweaking of compression level.

  • Transparency support for saved image data.

  • Background multithreaded image processing for better performance and instant format conversion.

  • Estimation of future image file size prior to it actual saving.

  • Proportional image resizing.

  • Aimed image zooming in Image Viewer.

  • More Tone Mapping algorithms to choose from.

  • More color correction options, such as Gamma correction, Brightness & Contrast adjustment, Hue & Saturation colors altering, and more.

  • Various user interface modes, such as Standard, Simplified and Professional, for a better user experience.

  • Bulk image converter.

  • Image to PDF conversion.

  • SVG as a source format with support for SVG vector data to Base64 vector data conversion.


The basic idea behind this web application was to provide accessible cross-platform service for those who need to open 32-bit images. To give practical answer on how to open and view hdr photos, on how to open hdr or exr files. On Windows, Linux, iOS, Android or iPhone devices. And not just open somehow, but do it in a quick and easy way without having to download and install any hdr file opener locally. The idea to bring desktop applications experience to the web as well as on mobile, such as a smartphones or tablets.

Thus, initial goal was to made a simple image viewer able to open *.exr and *.hdr images in a browser. However, during planning and development it quickly became clear that there is no reason to limit functionality to only 32-bit HDR images. Conventional 8-bit image formats require the same functionality and are even more popular. As follows, this online HDR file viewer, became a general purpose online image viewer, which in turn, has a great bonus, it can open and process EXR and HDR files.

But more importantly, it also became apparent that it has potential to close a gap in free online image processing services with user-friendly interface and multi-functionality. Most of existed ones either have a very limited functionality or there are great online image processing tools do exists, but they are too complex for non-professional users to handle. Simply put, capable but convenient and easy to understand online image editors are the missing chain. At least, we do not know any service of such. Therefore, we have a plan to gradually turn this online image viewer into online image editor.

Eventually, it should become an advanced online image editor with tools for color correction, image cropping, and so on. But at the same time with a very simple user interface, without excessive complexity that require a long learning curve, with no very specialized features that most people never use. Easy to use, only what you need.

See roadmap with current development plans for more information, but keep in mind that it may change over time.

Image Convert Ninja - Free online image converter with HDRI support.

Image Convert Ninja - Free 32bit to 8bit Image Converter application is created and maintained by RenderSnail.

It written in JavaScript using Three & React libraries for the core and interface. All necessary modules are already supplied with the page, so this web app is plug-in free and work directly in your browser. No need to install anything extra.

Feel free to ask for new features that you need and that you want to see here, we are always open to new ideas. You may have any suggestions or questions about this program, or you may have encountered an error while using it, please let us know.


v2.1.0 (Mar 17, 2023 Update)

  • Image Viewer navigation controls like Zoom and Pan are now locked by default. This will improve the experience of using Image Viewer on mobile devices by allowing users to easily scroll the page by swiping up and down, including across Image Viewer, without interfering with controls.

  • Image Viewer now has a button with a lock icon in the lower left corner. You may use it to lock and unlock Image Viewer controls.

v2.0.0 (Mar 11, 2023 Update)

  • The tool has been renamed from "Online Image Converter HDR" to "Image Convert Ninja". Having said that, this program is clearly now more about converting images than viewing them. But, Ninja continues to view images.

  • The Image Viewer itself has been significantly redesigned. Separate "Full Screen" and "Reset View" buttons have been removed. The full-screen mode capability has been eliminated entirely. Reset View, on the other hand, has developed into a double-click option. By double-clicking anywhere on the Image Viewer, you can now simply reset the view.