In Photoshop design, the Gradient and Paint Bucket tools are fundamental and frequently used color filling tools, especially common in web design, poster creation, and UI interface design. This article will provide detailed explanations of these two tools' functions, operation steps, core options, and practical techniques to help beginners quickly master and apply them flexibly.

1. Gradient Tool (Core Tool in Photoshop Design)

The core function of the Gradient tool is to create gradually changing color effects, achieving smooth transitions from one color to another (or multiple) colors. In practical design, gradient effects can be created directly with the Gradient tool or set in layer styles (the latter being more convenient for later modifications and more frequently used).

1.1 Default Gradient Settings and Basic Operations in Photoshop

Photoshop comes with various preset gradient schemes that can be used directly without manual adjustment. The specific operation steps are as follows:

1. Select the "Gradient Tool" in the left toolbar (shortcut key: G);
2. The top common bar will display the relevant settings of the Gradient tool. Click the gradient thumbnail (pointed by the left red arrow in the original diagram) to pop up the "Gradient Preset List";
3. Select the desired gradient in the list (e.g., "Red, Green" gradient). If the target gradient is not found, click the "Settings Icon" in the upper right corner of the list and choose "Reset Gradients" to restore default presets;
4. After selecting the gradient, click the first "Linear Gradient" in the "Gradient Style" of the common bar;
5. Create a new blank image (shortcut key: Ctrl+N) and drag on the canvas while holding down the left mouse button. After releasing, a linear gradient effect will be generated.

The default parameters in the common bar at this time are:

• Mode: Normal
• Opacity: 100%
• "Reverse" and "Transparent Areas" unchecked
• "Dither" checked

1.2 Key Characteristics of Gradient Lines (Range, Direction, and Color Distribution)

Many beginners wonder: "Why can the final gradient cover the entire canvas when the dragged gradient line doesn't fill the screen?" This requires understanding the core function of the gradient line - defining the color change range rather than the fill range. The specific rules are as follows:

1.2.1 Gradient Fill Range: Prerequisite for Full Canvas Coverage

Note: Unless there is a selection or mask in the canvas, the gradient effect will always fill the entire canvas. Regardless of whether the dragged gradient line covers the canvas, the final gradient will automatically expand to the full canvas.

1.2.2 The "Color Change Range" Function of Gradient Lines

The length of the gradient line only determines the "transition interval from start point to end point". Areas outside this interval will be filled with solid colors:

• The "start point" of the gradient line (where the mouse is pressed, displayed as a solid crosshair): corresponds to the "starting color". Areas outside the start point are filled with the starting color;
• The "end point" of the gradient line (where the mouse is released, displayed as a dashed crosshair): corresponds to the "ending color". Areas outside the end point are filled with the ending color;
• The area between start and end points: presents a smooth transition color from the starting color to the ending color.

Practical Verification Method:

1. Create a new image and drag a short gradient line while holding Shift (maintaining horizontal/vertical or 45° integer angle);
2. Open the "Info Panel" (shortcut key: F8) and move the mouse horizontally on the canvas;
3. Observe the color readings on the Info panel:
   • Within the gradient line range: color readings continuously change (transition colors);
   • Outside the gradient line range: color readings are fixed (starting color or ending color).

1.2.3 Impact of Gradient Direction on Color Distribution

The dragging direction of the gradient line directly determines the color distribution order:

• Dragging from left to right: generates a gradient with "left starting color, right ending color" (e.g., left red, right green);
• Dragging from right to left: generates a gradient with "left ending color, right starting color" (e.g., left green, right red).

1.3 5 Common Gradient Styles and Their Detailed Effects

Photoshop provides 5 core gradient styles, each with different color distribution patterns and application scenarios. The following are detailed explanations:

1. Linear Gradient (Most Basic Style)

• Characteristics: Linear color transition along the gradient line direction (any angle);
• Color Distribution: Gradient from start to end along a straight line, with areas outside both ends filled with starting and ending colors respectively;
• Application Scenarios: Background gradients, text gradients, graphic light/dark transitions (such as button highlights).

2. Radial Gradient

• Characteristics: Centered at the gradient start point, with the distance from start to end as the radius, spreading outward in a circular gradient;
• Color Distribution:
  • Within the radius range: Color transitions from starting color to ending color along each radial direction;
  • Outside the radius range: The entire canvas is filled with ending color;
  • Key Rule: Colors are the same on concentric circular arcs (e.g., each point on a yellow arc has the same color, each point on a blue arc has the same color). Blue arcs are closer to the starting color, yellow arcs are closer to the ending color;
• Application Scenarios: Circular icon gradients, light spot effects, color representation of circular objects like sun/moon.

3. Angle Gradient

• Characteristics: Centered at the gradient start point, with the line connecting start and end as the "starting angle", creating a clockwise circular gradient;
• Key Difference: The only style among all gradient styles "not affected by the distance between start and end points", with the gradient range determined only by angle;
• Color Distribution: Each ray originating from the start point has the same color (e.g., each point on a yellow ray has the same color, each point on a blue ray has the same color). Blue rays are closer to the starting color, yellow rays are closer to the ending color;
• Application Scenarios: Radar charts, dial gradients, rotating light effects (such as neon rings).

4. Symmetrical Gradient

• Characteristics: Can be understood as "two radial gradients in opposite directions merged", creating gradients simultaneously in opposite directions from the start point;
• Color Distribution:
  • From the start point to the end points in two opposite directions: Present transitions from starting color to ending color respectively;
  • Areas outside both end points: Filled with ending color;
  • Key Rule: Positions equidistant from the start point have the same color regardless of direction;
• Usage Note: If the gradient line fills the canvas, it will obscure the gradient effect on one side. Sufficient space must be reserved to display the bidirectional gradient;
• Application Scenarios: Symmetrical graphic gradients (such as butterfly wings), reflection effects, symmetrical light effects.

5. Diamond Gradient

• Characteristics: A "diamond-shaped range gradient" diffusing from the start point, similar to radial gradient but in a diamond shape;
• Diamond Generation Rule: With the line segment from start to end as one edge of the diamond, the other three edges are formed by rotating this segment 90°, 180°, and 270° respectively around the start point;
• Color Distribution:
  • Within the diamond range: Color transitions from starting color to ending color along the edge directions;
  • Outside the diamond range: Filled with ending color;
  • Key Rule: At equal distances from the start point, only colors on the 4 edges of the diamond are the same. Colors differ in areas between edges;
• Application Scenarios: Square icon gradients, diamond light effects, diamond decorative elements.

1.4 Core Option Functions of the Gradient Tool (Reverse, Dither, Transparent Areas)

In the Gradient tool's common bar, the three options "Reverse," "Dither," and "Transparent Areas" can further optimize gradient effects. Specific functions are as follows:

1.4.1 Reverse Option

• Function: Reverses the "color sequence" of the gradient, including the starting color, ending color, and all intermediate transition colors;
• Example: If the original gradient sequence is "Red→Green→Yellow→Blue," checking "Reverse" changes it to "Blue→Yellow→Green→Red";
• Application Scenario: Quickly switch primary and secondary colors of the gradient without re-editing the gradient preset.

1.4.2 Dither Option

• Function: In situations with fewer colors, generates intermediate transition colors through algorithms to reduce "gradient banding" (inconsistent color transition stripes) and make gradients smoother;
• Note: Detailed operations and advanced applications of this function will be further explained in the subsequent gradient editing section. Beginners are advised to keep it checked by default to ensure gradient quality.

1.4.3 Transparent Areas Option

• Function: Controls whether the gradient retains the transparency settings in the preset;
• Comparison of Two Effects (using "Transparent Rainbow" gradient + black background as an example):
  • "Transparent Areas" checked: The start and end areas of the gradient appear transparent, showing the black background below;
  • "Transparent Areas" unchecked: Transparent parts are filled with solid color, and the black background cannot be seen;
• Note: If the gradient preset itself doesn't contain transparency settings, checking this option makes no difference. Custom editing of transparency will be explained in subsequent sections.

2. Paint Bucket Tool (Quick Fill Tool in Photoshop)

The core function of the Paint Bucket tool is to quickly fill specified areas with color or patterns, essentially equivalent to "creating a selection with the Magic Wand tool and immediately filling it," but with simpler operations suitable for simple color filling scenarios.

2.1 Core Functions and Operations of the Paint Bucket Tool

• Fill Content: Supports two modes -
  1. Foreground Color Fill: Fill with the currently set foreground color (shortcut fill: ALT DELETE/ALT BackSpace);
  2. Pattern Fill: Fill with preset or custom patterns. If the fill area is larger than the pattern, it will automatically tile (same effect as the Pattern Stamp tool);
• Operation Steps:
  1. Select the "Paint Bucket Tool" (in the same group as the Gradient tool, shortcut key: G, press Shift+G to switch);
  2. Set parameters in the top common bar (mode, tolerance, opacity, etc.);
  3. Click the area on the canvas that needs to be filled to complete the fill.

2.2 Key Option Descriptions for the Paint Bucket Tool

The options of the Paint Bucket tool are similar to those of the Magic Wand tool, with added "Pattern Fill" and "All Layers" options. Details are as follows:

2.3 Alternative Solutions for the Paint Bucket Tool (More Efficient Fill Methods)

Due to the poor editability of the Paint Bucket tool (requiring refilling to modify colors/patterns), it's less commonly used in professional design today. The following 3 alternative methods are more recommended for higher flexibility:

1. Shortcut Key Fill for Foreground/Background Colors:
   • Fill with foreground color: ALT DELETE/ALT BackSpace;
   • Fill with background color: Ctrl DELETE/Ctrl BackSpace;
   • Advantage: No tool selection needed, one-step completion of fill, suitable for simple solid color fills.
2. Create Fill Layers (Solid Color/Pattern):
   • Operation path: Layer → New Fill Layer → Solid Color/Pattern;
   • Advantage: Extremely editable. To modify colors/patterns later, simply double-click the fill layer thumbnail to adjust, and layer masks can control the fill range.
3. Layer Style Fill:
   • Operation path: Double-click the blank space to the right of the layer thumbnail → Select "Color Overlay" (solid color) or "Pattern Overlay" (pattern);
   • Advantage: Can be combined with other layer styles (such as drop shadow, glow) and doesn't destroy the original layer content, suitable for overlaying layer effects in design.