[{"data":1,"prerenderedAt":60},["ShallowReactive",2],{"/2025/09/22-black-background-on-combined-images":3},{"id":4,"title":5,"body":6,"date":51,"description":47,"extension":52,"meta":53,"navigation":54,"path":55,"robots":56,"seo":57,"stem":58,"__hash__":59},"posts/2025/09/22 black-background-on-combined-images.md","22 Black Background On Combined Images",{"type":7,"value":8,"toc":48},"minimark",[9,18,25,28,31,34],[10,11,13],"post-title",{":date":12},"date",[14,15,17],"h1",{"id":16},"black-background-on-combined-images","Black Background on Combined Images",[19,20,21],"notes",{},[22,23,24],"p",{},"This is a repost from my old blog. First posted in 11/30/2016.",[26,27],"br",{},[22,29,30],{},"I was asked to research about a strange behavior when we combine two images, each image becomes small and the rest of the extra space is filled with black color. After doing a bit of research and making sample applications, I found out that it has something to do with image dpi.",[22,32,33],{},"Each image is scanned with 240 dpi while Windows default to 96 dpi. That means, the image is scaled down, so I simply get the least dpi and set it as dpi for the combined image. It works for now, though I can see the potential problem if somehow the horizontal and vertical dpi are different.",[35,36,37],"code-block",{},[38,39,44],"pre",{"className":40,"code":42,"language":43},[41],"language-text","Dim image1 As Bitmap = ...(code to get image) --> has 240 dpi\nDim image2 As Bitmap = ...(code to get image) --> has 240 dpi\n\nDim combinedImage As New Bitmap(...) --> default to 96 dpi\n\nDim horizontalResolution As Single = Math.Min(image1.HorizontalResolution, image2.HorizontalResolution)\nDim verticalResolution As Single = Math.Min(image1.VerticalResolution, image2.VerticalResolution)\n\ncombinedImage.SetResolution(horizontalResolution, verticalResolution)\n","text",[45,46,42],"code",{"__ignoreMap":47},"",{"title":47,"searchDepth":49,"depth":49,"links":50},2,[],"2025-09-22T00:00:00.000Z","md",{},true,"/2025/09/22-black-background-on-combined-images",null,{"title":5,"description":47},"2025/09/22 black-background-on-combined-images","4m6xbiueZ-IVzOZ1KD4B6AlOv5AA_VUrtVSNz2Rwn0Y",1785167453085]