Differences

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--- saving_20a_20jpeg_20image [2018/03/31 13:19] – external edit 127.0.0.1
+++ saving_20a_20jpeg_20image [2024/01/05 00:21] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
 =====Saving a JPEG image=====
-//by Richard Russell, December 2006//\\ \\  The main BBC BASIC for Windows documentation explains how to [[http://www.bbcbasic.co.uk/bbcwin/manual/bbcwine.html#gifjpeg|display a JPEG image]] and elsewhere you can find out how to [[/Displaying%20a%20JPEG%20or%20GIF%20in%20a%20picture%20box|load a JPEG image]] for use in your program. This article describes how to **save** an image as a JPEG file. It relies on the presence of the //GDI Plus// library so will work only on Windows XP (or later) or if you have specifically installed **GDIPLUS.DLL** on the target computer. Microsoft permits you to redistribute this file so you can include it with your program if necessary.\\ \\  To begin with you need to have a **handle** to the bitmap you want to save (see below if instead the bitmap is in the form of a **DIB**). One way of obtaining a handle is to load the image from a file (e.g. a BMP file):\\ \\
+//by Richard Russell, December 2006//\\ \\  The main BBC BASIC for Windows documentation explains how to [[http://www.bbcbasic.co.uk/bbcwin/manual/bbcwine.html#gifjpeg|display a JPEG image]] and elsewhere you can find out how to [[/Displaying%20a%20JPEG%20or%20GIF%20in%20a%20picture%20box|load a JPEG image]] for use in your program. This article describes how to **save** an image as a JPEG file. It relies on the presence of the //GDI Plus// library so will work only on Windows XP (or later) or if you have specifically installed **GDIPLUS.DLL** on the target computer. Microsoft permits you to redistribute this file so you can include it with your program if necessary.\\ \\  To begin with you need to have a **handle** to the bitmap you want to save (see below if instead the bitmap is in the form of a **DIB**). One way of obtaining a handle is to load the image from a file (e.g. a BMP file):
+<code bb4w>
         bmpfile$ = "\Windows\Soap Bubbles.bmp"
         SYS "LoadImage", 0, bmpfile$, 0, 0, 0, 16 TO hbitmap%
-Here the image is loaded at its original size. You can alternatively scale the image to different dimensions:\\ \\
+</code>
+Here the image is loaded at its original size. You can alternatively scale the image to different dimensions:
+<code bb4w>
         bmpfile$ = "\Windows\Soap Bubbles.bmp"
         SYS "LoadImage", 0, bmpfile$, 0, dx%, dy%, 16 TO hbitmap%
-Where **dx%** and **dy%** are the wanted width and height of the image respectively (the scaling quality is not particularly good so for best results you might prefer to scale the image using a third-party program).\\ \\  There are a number of other ways in which you might obtain a bitmap handle, which are outside the scope of this article. You can easily obtain a handle to whatever is displayed in your program's output window:\\ \\
+</code>
+Where **dx%** and **dy%** are the wanted width and height of the image respectively (the scaling quality is not particularly good so for best results you might prefer to scale the image using a third-party program).\\ \\  There are a number of other ways in which you might obtain a bitmap handle, which are outside the scope of this article. You can easily obtain a handle to whatever is displayed in your program's output window:
+<code bb4w>
         SYS "GetCurrentObject", @memhdc%, 7 TO hbitmap%
-but this ordinarily returns the //entire// 1920 x 1440 bitmap which is probably not what you want. To save just a region of your program's output window the easiest way is probably to save it first as a BMP file (using ***GSAVE**) then load it using LoadImage as shown above.\\ \\  Once you've got a handle to the bitmap you simply save it as a JPEG file as follows:\\ \\
+</code>
+but this ordinarily returns the //entire// 1920 x 1440 bitmap which is probably not what you want. To save just a region of your program's output window the easiest way is probably to save it first as a BMP file (using ***GSAVE**) then load it using LoadImage as shown above.\\ \\  Once you've got a handle to the bitmap you simply save it as a JPEG file as follows:
+<code bb4w>
         PROCsavejpeg(hbitmap%, filename$, quality%)
-Here **filename$** is the name of the JPEG file to create and **quality%** is a measure of relative quality from 1 (bad) to 100 (good). The better the quality the larger the file that will be created.\\ \\  One you've saved the file you should delete the bitmap handle:\\ \\
+</code>
+Here **filename$** is the name of the JPEG file to create and **quality%** is a measure of relative quality from 1 (bad) to 100 (good). The better the quality the larger the file that will be created.\\ \\  One you've saved the file you should delete the bitmap handle:
+<code bb4w>
         SYS "DeleteObject", hbitmap%
-Finally, here's the code for **PROCsavejpeg** itself:\\ \\
+</code>
+Finally, here's the code for **PROCsavejpeg** itself:
+<code bb4w>
         DEF PROCsavejpeg(hbitmap%, filename$, quality%)
         LOCAL gdiplus%, ole32%
@@ Line 68: / Line 90: @@
         ENDPROC
-\\  If, instead of a bitmap **handle**, you have a bitmap (DIB) stored in memory you can use this alternative routine:\\
+</code>
+If, instead of a bitmap **handle**, you have a bitmap (DIB) stored in memory you can use this alternative routine:
+<code bb4w>
         DEF PROCsavejpegdib(dib%, bmi%, filename$, quality%)
         LOCAL gdiplus%, ole32%
@@ Line 123: / Line 150: @@
         ENDPROC
-\\  You would call it as follows:\\
+</code>
+You would call it as follows:
+<code bb4w>
         PROCsavejpegdib(dibits%, bmi{}, filename$, quality%)
+</code>
 where **dibits%** is the address of the bitmap data and **bmi{}** is a BITMAPINFO structure containing the dimensions etc. and (optionally) colour palette for the bitmap.