I *have* tried, Richard. It is not returning the state of the file. Files that Irfanview recognizes are prograssive, your example code does not. Looking at C code in gd-2.0.33/gd_jpeg.c downloaded from http://www.boutell.com/gd/ there is a comment: /* REMOVED by TBB 2/12/01. This field of the structure is documented as private, and sure enough it's gone in the latest libjpeg, replaced by something else. Unfortunately there is still no right way to find out if the file was progressive or not; just declare your intent before you write one by calling gdImageInterlace(im, 1) yourself. After all, we're not really supposed to rework JPEGs and write them out again anyway. Lossy compression, remember? */ The docs at http://www.boutell.com/gd/manual2.0.33.html#gdImageInterlace say gdImageInterlace is used to determine whether an image should be stored in a linear fashion, in which lines will appear on the display from first to last, or in an interlaced fashion, in which the image will "fade in" over several passes. By default, images are not interlaced. (When writing JPEG images, interlacing implies generating progressive JPEG files, which are represented as a series of scans of increasing quality. Noninterlaced gd images result in regular [sequential] JPEG data streams.) A nonzero value for the interlace argument turns on interlace; a zero value turns it off. Note that interlace has no effect on other functions, and has no meaning unless you save the image in PNG or JPEG format; the gd and xbm formats do not support interlace. When a PNG is loaded with gdImageCreateFromPng or a JPEG is loaded with gdImageCreateFromJpeg, interlace will be set according to the setting in the PNG or JPEG file. -------------- To me that means the code authors cannot determine what the state of the file is, and are not returning a state they cannot determine. Gerry On 1/25/07, Richard Lynch <ceo@xxxxxxxxx> wrote:
Re-read the docs more carefully. The second arg is optional, and it returns the PRIOR state of the interlaced-ness (or progressive-ness for a JPEG). Standard computer-science function trick to return prior state when altering state, and to simply return state if the second arg is not passed in. So if you do not pass in a second arg, you should be getting the state of the JPEG. Try it. On Wed, January 24, 2007 7:20 pm, Gerry Danen wrote: > Richard, > > imageinterlace() turns the interlace bit on or off. It only returns 1 > if you set it to 1 as the second parameter...
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