In Photoshop and various image creation workflows, the choice of image format directly affects the editability, display quality, and compatibility of your work. This article will start from the fundamental differences between raster and vector images, and provide a detailed analysis of format selection principles during creation, saving strategies for different scenarios, and methods for setting file extensions. This will help you efficiently complete image creation and output.

1. Core Differences Between Raster and Vector Images: Why Can't We Just Use Vector Formats?

From a technical perspective, raster and vector images each have their own characteristics. Vector formats cannot completely replace raster formats, with the core reason being their different capabilities and efficiencies in handling "color complexity."

1. Limitations of Vector Images: Computational Bottlenecks in Complex Color Scenarios

Vector images are generated based on line segments and mathematical coordinates. Their advantage lies in scalability without distortion, but they have clear limitations when recording color-complex images (such as landscape photos or portraits):

• If using vector format to record such images, each scene element (such as fabric folds on clothing or leaves of background flowers) would need to be broken down into countless line segments, with color information defined for each segment.
• This creates enormous computational load, which current personal computers struggle to process efficiently. Even if processing completes, the resulting vector file size would be exceptionally large, making it impractical for real-world use.

2. Advantages of Raster Images: Simple and Efficient Color Recording

Raster images (also known as pixel images) are generated by "scanning and recording colors pixel by pixel," which perfectly compensates for the shortcomings of vector formats in complex color scenarios:

• Simple principle: No need for complex line segmentation or coordinate calculations; directly records color values for each pixel, resulting in minimal computational load.
• Efficient storage: Can quickly save color-rich images, which is why digital cameras, scanners, and similar devices default to outputting raster images - these devices' core requirement is "rapidly capturing real-world scene colors," which raster formats perfectly match.

3. Special Scenarios: When Do Vector Images Contain Less Information?

Vector images are not "bulky" in all scenarios. When images meet the "single-color" condition, vector formats' advantages become apparent:

• For example, a solid-color straight line: vector format only needs to record start point, end point coordinates, and a single color, resulting in much smaller file size than raster format (raster needs to record the color of each pixel on the line).
• Conversely, if each pixel on the line has a different color (such as gradient-colored lines), vector format needs to recalculate coordinates for each color change, making its file size and computational load far exceed that of raster format.

4. Creative Advantages of Vector Images: Achieving Color Richness

It's important to note that vector formats being "unsuitable for complex colors" refers to image acquisition scenarios (such as photography or scanning). In active creation scenarios, vector images can achieve rich colors through "regional drawing + color filling":

• For example, when tracing photos in Illustrator to create vector mouse images, the mouse can be divided into multiple parts like "shell, buttons, scroll wheel," each drawn and filled with color separately, then integrated into a complete image.
• Professional designers can even achieve "photorealistic effects" through meticulous vector drawing, suitable for scenarios requiring high scaling precision like logo design and icon creation.

2. Image Format Selection During Creation: Prioritizing "Editability"

During the image creation phase (rather than final saving phase), the core principle of format selection is: maximizing editability retention - this directly determines the flexibility of subsequent editing.

1. Core Manifestation of Editability: Scaling and Editing Freedom

• Vector images: No pixelation when scaling; line segments and color parameters can be adjusted at any time, making editability far superior to raster images.
• Raster images: Pixelation occurs when enlarged beyond a certain proportion, and modifying local colors (such as adjusting part of an outline) easily damages overall pixel structure, resulting in poor editability.

2. Format Collaboration in Photoshop and Illustrator

• Both support coexistence of "raster + vector" images: For example, in Photoshop, vector shapes (such as text or graphic paths) can be inserted while retaining raster layers (such as photo materials).
• Convenience of format conversion: Vector images can be easily converted to raster images (such as exporting to JPG in Illustrator); however, converting raster images to vector images is more difficult (requires functions like "image tracing," with accuracy depending on original image quality).

3. Format Selection Recommendations During Creation

• Prioritize vector formats: Especially when creating elements that need "repeated scaling or outline modification" (such as logos, title text, mask paths), vector formats ensure subsequent editing without quality loss.
• Combine with raster formats: For "color-complex materials that don't require frequent modification" (such as photo backgrounds), raster formats can be retained to avoid unnecessary computational load.

3. Image Saving Format Strategy: Balancing Editability and Compatibility

After creation is complete, appropriate saving formats should be chosen based on "subsequent usage" - the core goal is "either retain editability or ensure others/devices can open normally."

1. First, Understand a Key Fact: All Display Devices Are Raster

Regardless of whether raster or vector formats are used during creation, they are ultimately converted to raster when displayed on devices:

• Mainstream media like monitors (CRT, LCD, plasma) and films (composed of continuous still raster frames) all present images in raster format.
• This also explains "why vector images still have value": Their advantages lie in editability during the creation process, not in final display effects.

2. Prioritize Saving in Software-Specific Formats: Retaining Complete Editing Information

The core function of software-specific formats is to retain all editable information (such as layers, paths, adjustment parameters), forming the basis for subsequent editing:

• Photoshop's specific format: PSD format, which preserves layers, masks, text styles, and all editing traces, allowing any detail to be modified when reopened.
• Illustrator's specific format: AI format, which retains vector paths, color panels, and layer structures, supporting further adjustment of vector elements.
• Adobe software format compatibility: PSD, AI, and other formats can be used across software. For example, PSD files with transparency effects created in Photoshop can be directly imported into Adobe Premiere for video compositing without readjusting transparency parameters.

3. Applicable Scenarios for Universal Formats: Easy Sharing and Display

When sharing images with others (who may not have professional software installed), universal formats supported by operating systems or mainstream software by default should be chosen:

• Windows systems: Prioritize BMP format, which is supported by default for display and can be opened without additional software.
• MacOS systems: Prioritize TIFF format, which offers strong compatibility and supports higher color depth (suitable for professional image display).
• Limitations of universal formats: They don't contain editable information. For example, when saving PSD as JPG, layer information is completely lost, making it impossible to adjust individual layers separately.

4. Exclusive Format Selection for Web Scenarios

For works intended for web display, web-specific image formats should be chosen - PSD or AI formats cannot be displayed directly on websites. Common formats include:

• JPG (JPEG/JPE): Suitable for color-rich photographic images, supports compression (balancing quality and file size), and is the preferred format for web photos.
• GIF: Supports only 256 colors, suitable for simple graphics (such as icons, animations), supports transparent backgrounds, and is commonly used for web icons or dynamic elements.
• PNG: Supports full color and transparent backgrounds, with lossless (or low-loss) image quality, suitable for images requiring high clarity and transparency effects (such as logos, product screenshots).

4. File Extension Settings: How to Display Format Identifiers?

File extensions (letters after ".", such as "jpg" in "sample.jpg") are direct basis for determining image formats. However, Windows systems hide known format extensions by default, potentially causing format misjudgment (such as "shop.bmp" only displaying as "shop"). Here are the steps to display extensions:

1. Open Windows "Folder Options": Can be accessed through "Control Panel" → "Folder Options," or in any folder window, click "Tools" menu → "Folder Options."
2. Switch to the "View" tab: Find the "Hide extensions for known file types" option in the "Advanced settings" list.
3. Uncheck this option: Ensure the checkbox before "Hide extensions for known file types" is unchecked.
4. Apply settings: Click "Apply" → "OK," and all files will now display complete extensions (such as "excell.psd" "sample.png"), making format identification quick and easy.

5. Summary: Core Logic of Image Format Selection

1. Creation phase: Prioritize vector formats (retaining editability), combine with raster formats for handling complex color materials, and make good use of PS and AI format collaboration features.
2. Saving phase: First save in proprietary formats (PSD/AI, preserving editing traces), then save in universal formats based on usage (BMP/TIFF for sharing, JPG/GIF/PNG for web).
3. Format identification: Enable file extension display to avoid compatibility issues caused by format misjudgment.