检查文件是否为图片

Question

我构建了一种从文件向卡片添加图像并将其存储在自定义属性中的方法。这很好用。

 answer file tImageDialogTranslations with type "Images|jpg|jpeg|png"
 if  it is not empty then
  put  it into tMyImagePath

  put url("binfile:" & tMyImagePath) into tMyImage
  put base64encode( tMyImage) into tBase64ImgData

  # store image in cust prop
  set the cImageBlob of img "img_collection_picture" to  tBase64ImgData 

  #show image
  put base64decode(tBase64ImgData) into tShowImage
  set the text of image "img_collection_picture" to tShowImage
 end if

遗憾的是，当我在文件答案对话框中添加 * 时，我还可以选择另一种文件类型，例如 txt，然后存储在自定义属性中，但不会显示在图片。

如何检查用户是否真的选择了有效的图像文件？

Answer 1

我认为您可以通过检查文件扩展名或文件的幻数来验证。这些信息可以帮助您确定该文件是否为图像文件。扫描文件内容以验证它是否是图像文件不是一个好主意。

Answer 2

我弄明白了，我想我会分享整个相关部分：

answer file tImageDialogTranslations with type "Images|jpg,jpeg,png,gif"
if it is not empty then
  put  it into tMyImagePath
  put url("binfile:" & tMyImagePath) into tMyImage
  put binarydecode("H8",tMyImage,tMyImageHex) -- to check if it is actually an image
  put base64encode( tMyImage) into tBase64ImgData


  set the itemdel to comma
    if tMyImageHex is among the items of "ffd8ffe0,47494638,89504e47"  then

     ### store image in custom property
     set the cImageBlob of img "img_collection_picture" to  tBase64ImgData 

     ### now display image in field
     put base64decode(tBase64ImgData) into tShowImage
     set the text of image "img_collection_picture" to tShowImage

    else
     # do nothing / error 100499
     answer "Error 100499: Please choose an image file. "
    end if

 else
     # do nothing since no file was chosen
 end if

检查文件是否为图片

Check if file is an image

image

livecode