修复登录及验证码功能

go/pkg/captcha/captcha.go

@@ -1,6 +1,7 @@
 package captcha
 
 import (
+	"bytes"
 	"context"
 	"crypto/rand"
 	"encoding/base64"
@@ -69,20 +70,23 @@ func drawImage(code string) image.Image {
 	bg := color.RGBA{240, 245, 255, 255}
 	draw.Draw(img, img.Bounds(), &image.Uniform{bg}, image.Point{}, draw.Src)
 
-	for i := 0; i < 4; i++ {
+	for i := 0; i < 3; i++ {
 		x1, _ := rand.Int(rand.Reader, big.NewInt(int64(width)))
 		y1, _ := rand.Int(rand.Reader, big.NewInt(int64(height)))
 		x2, _ := rand.Int(rand.Reader, big.NewInt(int64(width)))
 		y2, _ := rand.Int(rand.Reader, big.NewInt(int64(height)))
 		drawLine(img, int(x1.Int64()), int(y1.Int64()), int(x2.Int64()), int(y2.Int64()), randomColor())
 	}
-	for i := 0; i < 30; i++ {
+	for i := 0; i < 25; i++ {
 		x, _ := rand.Int(rand.Reader, big.NewInt(int64(width)))
 		y, _ := rand.Int(rand.Reader, big.NewInt(int64(height)))
 		img.Set(int(x.Int64()), int(y.Int64()), randomColor())
 	}
+	// 字符居中绘制：字符高 21px (7*3)，画布高 40px，垂直居中起始 y 约 9px；4 字符总宽 90px，水平居中起始 x 为 15px
 	for i, ch := range code {
-		drawChar(img, 15+i*25, 28, string(ch), randomDarkColor())
+		offsetY, _ := rand.Int(rand.Reader, big.NewInt(3))
+		charY := 8 + int(offsetY.Int64()) // 8..10px，垂直完美居中
+		drawChar(img, 15+i*25, charY, string(ch), randomDarkColor())
 	}
 	return img
 }
@@ -134,7 +138,7 @@ func drawChar(img *image.RGBA, x, y int, ch string, c color.Color) {
 			if px == '1' {
 				for dy := 0; dy < scale; dy++ {
 					for dx := 0; dx < scale; dx++ {
-						img.Set(x+col*scale+dx, y-row*scale-7*scale+dy, c)
+						img.Set(x+col*scale+dx, y+row*scale+dy, c)
 					}
 				}
 			}
@@ -192,7 +196,9 @@ func randomDarkColor() color.RGBA {
 }
 
 func encodeToBase64(img image.Image) string {
-	var buf strings.Builder
-	png.Encode(base64.NewEncoder(base64.StdEncoding, &buf), img)
+	var buf bytes.Buffer
+	enc := base64.NewEncoder(base64.StdEncoding, &buf)
+	_ = png.Encode(enc, img)
+	_ = enc.Close()
 	return buf.String()
 }

go/pkg/captcha/captcha_test.go

@@ -0,0 +1,33 @@
+package captcha
+
+import (
+	"bytes"
+	"encoding/base64"
+	"image/png"
+	"strings"
+	"testing"
+)
+
+func TestDrawImageValidPNG(t *testing.T) {
+	img := drawImage("ABCD")
+	b64 := encodeToBase64(img)
+	data, err := base64.StdEncoding.DecodeString(b64)
+	if err != nil {
+		t.Fatalf("base64 decode failed: %v", err)
+	}
+
+	decoded, err := png.Decode(bytes.NewReader(data))
+	if err != nil {
+		t.Fatalf("png decode failed: %v", err)
+	}
+
+	bounds := decoded.Bounds()
+	if bounds.Dx() != 120 || bounds.Dy() != 40 {
+		t.Fatalf("expected 120x40, got %dx%d", bounds.Dx(), bounds.Dy())
+	}
+
+	// Verify all characters in chars set can be drawn without panic
+	for _, ch := range chars {
+		_ = drawImage(strings.Repeat(string(ch), 4))
+	}
+}