Komprese obrázků online

What Komprese obrázků does

Image compression makes a file smaller so it uploads faster, loads quicker on a web page and fits the size limits of forms, email and chat apps. The picture is decoded to pixels and saved again with stronger compression.

JPG files are encoded with MozJPEG, which produces smaller files than standard JPG encoders at the same quality. PNG files are reduced to a palette of at most 256 colors, and the PNG Compressor can also optimize them without changing any pixel. If the result is not smaller and the format stays the same, you get the original file back.

Jak používat nástroj Komprese obrázků

1. Přetáhněte soubory, které chcete zmenšit.
2. Zvolte úroveň komprese, nebo ponechte doporučené nastavení.
3. Klikněte na Komprimovat a porovnejte původní a novou velikost souborů.
4. Stáhněte zmenšené soubory.

When to use Komprese obrázků

• Shrink phone photos of several megabytes before attaching them to an email or uploading them to a form with a size limit.
• Reduce product images and blog photos so web pages load faster and score better in page speed tests.
• Make PNG screenshots smaller for documentation, support tickets and chat messages while keeping the text easy to read.
• Prepare a batch of images for a website by limiting all of them to a maximum width, such as 1920 pixels.

Settings explained

Output format

Shown in the Image Compressor. Same as input keeps the format. Choosing WEBP or AVIF instead usually gives a much smaller file than JPG or PNG at similar visual quality.

Quality

Sets the compression strength for JPG, WEBP and AVIF, from 10 to 100. The default of 75 is a good balance; 60 to 70 gives smaller files for web use, and 85 or more suits printing.

Compression mode

Shown in the PNG Compressor. Smaller (lossy) reduces the image to a limited color palette and gives the biggest savings. Lossless keeps every pixel exactly and only optimizes how the data is stored.

Colors

Shown in Smaller (lossy) mode. Sets the palette size from 8 to 256 colors; the default is 256. Screenshots and graphics often look the same at 64 to 128 colors, while photos need 256.

Max width (0 = keep)

Scales down images that are wider than this number of pixels, keeping the aspect ratio. Narrower images are not enlarged. For web pages, 1600 to 2000 pixels is usually enough; 0 keeps the original size.

Format comparison

Co je PNG?

PNG (Portable Network Graphics) je obrazový formát z roku 1996, jehož autorem je W3C. Formát používá bezeztrátovou kompresi a podporuje průhlednost. Soubory mají příponu .png.

PNG was created in the mid-1990s as a free replacement for GIF, whose compression method was covered by patents at the time. It applies a filtering step and then compresses pixels with the DEFLATE algorithm, so every pixel is kept exactly. It supports full color, grayscale, palette images and a full alpha channel for smooth transparency.

PNG is the right choice for screenshots, logos, icons, diagrams, user interface graphics and any image with sharp edges, text or flat colors. It is also a safe format for images that need transparent backgrounds or will be edited again.

Because PNG is lossless, photos saved as PNG are often several times larger than the same photo saved as JPG or WebP. PNG has no lossy mode, and a standard PNG file cannot store animation.

PNG opens in every modern web browser, on Windows, macOS, Linux, Android and iOS, and in practically all image viewers, image editors, office suites and design tools. It is one of the most widely supported image formats.

Co je JPG?

JPG (Joint Photographic Experts Group) je obrazový formát z roku 1992, jehož autorem je JPEG. Formát používá ztrátovou kompresi a nepodporuje průhlednost. Soubory mají příponu .jpg nebo .jpeg.

JPG, also written JPEG, is named after the Joint Photographic Experts Group, which wrote the standard. It splits an image into small blocks, transforms each block with a discrete cosine transform and discards the fine detail that the eye notices least. A quality setting controls how much detail is removed and therefore the file size.

JPG is the standard choice for photographs and other images with smooth color gradients, such as camera pictures, product photos and images for email or social media. It gives small files with good visual quality at moderate settings.

JPG does not support transparency or animation. Each time a JPG is edited and saved again, it loses a little more quality. Text, line art and sharp edges can show visible blocks or halos at low quality settings.

JPG is supported everywhere: in all web browsers, on all desktop and mobile operating systems, and on cameras, phones and printers. All image editors and office programs open it. It is the most compatible format for sharing photos.

Co je WEBP?

WEBP (WebP) je obrazový formát z roku 2010, jehož autorem je Google. Formát podporuje ztrátovou i bezeztrátovou kompresi, podporuje průhlednost a umí ukládat animace. Soubory mají příponu .webp.

WebP was developed by Google to make images on the web smaller. Its lossy mode is based on the VP8 video codec, and it also has a separate lossless mode. Both modes can include an alpha channel for transparency. The format also supports animation, so it can replace JPG, PNG and GIF in many cases.

WebP is a good choice for images on websites and in apps, where smaller files load faster. It works for photos, graphics with transparency and short animations, often at a smaller size than JPG, PNG or GIF.

Some older software, image editors, print services and upload forms still do not accept WebP. Lossy WebP always reduces color resolution, which can blur fine colored detail. At very high quality settings, the size benefit over JPG can be small.

All current major browsers display WebP, including Chrome, Edge, Firefox and Safari on recent versions of macOS and iOS. Windows, macOS, Android and most modern image editors open it, but some older desktop programs do not.

Co je AVIF?

AVIF (AV1 Image File Format) je obrazový formát z roku 2019, jehož autorem je Alliance for Open Media. Formát podporuje ztrátovou i bezeztrátovou kompresi, podporuje průhlednost a umí ukládat animace. Soubory mají příponu .avif.

AVIF stores images compressed with the AV1 video codec inside a HEIF-based container. It was developed by the Alliance for Open Media, a group that includes major browser and technology companies, as a royalty-free format. It supports high bit depth, wide color, HDR, transparency and image sequences.

AVIF is best for web images where file size matters most. It often produces smaller files than JPG or WebP at similar visual quality, especially for photos, and it is useful for HDR and wide color images.

Encoding AVIF is slow compared with JPG or WebP, especially at high quality settings. Many image editors, older devices and upload forms do not accept it yet. Fine detail and texture can look smoothed at low quality settings.

Current versions of Chrome, Edge, Firefox and Safari display AVIF. Recent Windows, macOS, iOS and Android versions can open it, sometimes with an extra codec extension, but support in editors, office software and older systems is incomplete.

Proč používat nástroj Komprese obrázků od FansBond

Většina online převodníků nahrává vaše soubory na své servery. Nástroj „Komprese obrázků“ od FansBond místo toho pracuje přímo ve vašem prohlížeči díky WebAssembly a moderním rozhraním prohlížeče. Soubory zůstávají ve vašem zařízení, což je bezpečnější pro soukromé fotky, smlouvy i nezveřejněnou práci, a často je to i rychlejší, protože se nic nemusí nahrávat ani stahovat.

Žádné fronty, žádné vodoznaky a žádný účet. Jakmile se stránka načte, nástroj funguje i na pomalém připojení.

Tips for the best result

• Reducing the width often saves more than lowering the quality. A 4000-pixel phone photo shown at 1200 pixels wastes most of its data.
• Avoid compressing the same JPG again and again. Each save loses a little more detail, so always start from the original file.
• For photos saved as PNG, converting to JPG, WEBP or AVIF usually saves far more than any PNG setting, as long as you do not need transparency.
• Saving as JPG fills transparent areas with white. Keep PNG, WEBP or AVIF output for logos and graphics with a transparent background.

How Komprese obrázků works in your browser

When you add an image, the browser decodes it into raw pixels on your device. HEIC photos are decoded with a browser build of libheif, and AVIF with the libavif decoder. The pixels are then processed on an HTML canvas and encoded again in the format you picked.

JPG, PNG and WebP are encoded with your browser's built-in encoders, and AVIF with libavif compiled to WebAssembly. The compressors add MozJPEG for smaller JPG files and OxiPNG for lossless PNG optimization. Because everything runs locally, the speed depends on your device rather than on a server queue.

Privacy and security

Most online converters upload your files to a server, process them there and keep a copy for some time. Komprese obrázků works differently: the code is downloaded to your browser once, and your files are read and written only on your device.

You can check this yourself: after the page has loaded, turn off your internet connection and the tool still works. This makes it safe for contracts, IDs, medical records, private photos and unreleased work.