GDI Image Resize

Question:

Guido wrote several UDFs for GDI+ about a year ago (posted in the tech database). They have been very helpful, but now I need more...
I need to resize a jpg (basically create a large thumbnail). I have tried Pixie, but the JPG compression is way too high for the quality I need. The images need to be jpegs - not bmps - or compression would not be an issue. I also need it to be as fast as possible (there are thousands of jpgs to convert), so I thought GDI+ might be the way to go.

Has anyone tried to resize an image with GDI+?

Answer:

#definefunction gpGetImageThumbnail(agp, GpImage, thumbWidth, thumbHeight)
	bthumbImage = binaryalloc(4)
	r = dllcall(agp[0], long:"GdipGetImageThumbnail", long:GpImage, long:thumbWidth, long:thumbHeight, lpbinary:bthumbImage, lpnull, lpnull)
	thumbImage = binarypeek4(bthumbImage, 0)
	binaryfree(bthumbImage)
	
	if r==0 then return thumbImage
	else return 0
#endfunction 

to use it, in the JPEG encode example i posted do something like,

;load image
img = gpLoadImageFromFile(agp, inFile)

imgThumbnail = gpGetImageThumbnail(agp, img, 100, 100)

gpSaveImageToFile(agp, imgThumbnail, outFile, bJPEG, 50)

gpDisposeImage(agp, img)
gpDisposeImage(agp, imgThumbnail)

Note that all the code is omitted but i tested it and it works, you will need to do some math if you want to keep the aspect ratio. Reference: http://techsupt.winbatch.com/webcgi/webbatch.exe?techsupt/nftechsupt.web+WinBatch/Samples~from~Users+GDI~Image~Encoding.txt

- Guido

Article ID:   W17219

File Created: 2014:07:18:09:51:38

Last Updated: 2014:07:18:09:51:38

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GDI Image Resize

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