我有多個像這樣的網址，總是返回PNG圖像。https://hydro.nationalmap.gov/arcgis/rest/services/wbd/MapServer/export?bbox=-106.6462299999999885,25.83722399999999908,-93.50780600000010168,36.50038700000000347&size=640,519&bboxSR=4326&layers=show:4&f=image&transparent=true我想檢查從URL返回的圖像是否像上面的URL一樣都是空的（透明的），或者它里面有一些實際的圖像。我通過以下函數發出請求，并檢查HTTP狀態是否為200，返回的內容類型是否為圖像。我需要在此處添加功能以測試圖像是否為空。thumbnail := "https://hydro.nationalmap.gov/arcgis/rest/services/wbd/MapServer/export?bbox=-106.6462299999999885,25.83722399999999908,-93.50780600000010168,36.50038700000000347&size=640,519&bboxSR=4326&layers=show:4&f=image&transparent=true"resp, err := client.Get(thumbnail)if err != nil { fmt.Println(err)} else if resp.StatusCode == 200 && strings.HasPrefix(resp.Header["Content-Type"][0], "image") { return thumbnail} else { fmt.Println(thumbnail, resp.StatusCode, resp.Header["Content-Type"][0])}
1 回答
Smart貓小萌
TA貢獻1911條經驗 獲得超7個贊
標準庫提供了功能強大的軟件包和解碼器，使我們能夠非常輕松地做到這一點。imageimage/png
我們知道透明度意味著 alpha=0，我們需要做的就是迭代圖像的像素。
package main
import (
"image/png"
"io"
"log"
"net/http"
)
func main() {
transparentResp, _ := http.Get("https://upload.wikimedia.org/wikipedia/commons/3/3d/1_120_transparent.png")
defer transparentResp.Body.Close()
notTransparentResp, _ := http.Get("https://upload.wikimedia.org/wikipedia/commons/thumb/5/58/Pitch.png/640px-Pitch.png")
defer notTransparentResp.Body.Close()
println(isFullyTransparentPng(transparentResp.Body))
println(isFullyTransparentPng(notTransparentResp.Body))
}
func isFullyTransparentPng(reader io.Reader) bool {
img, _ := png.Decode(reader)
for x := img.Bounds().Min.X; x < img.Bounds().Dx(); x++ {
for y := img.Bounds().Min.Y; y < img.Bounds().Dy(); y++ {
_, _, _, alpha := img.At(x, y).RGBA()
if alpha != 0 {
return false
}
}
}
return true
}
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