IMG-24: load BMP via source (#1451)

* bmpload.c

* #ifdef VIPS_META_PALETTE

* int32 height/width

* Separate #ifdef for VIPS_META_BITS_PER_SAMPLE

* RLE fixes

* bufsize

* += fix

* Move rel to x

* Allocate load buffer in load()

vips/bmp.h

@@ -0,0 +1,30 @@
+/*
+ * BMP save/load
+ */
+#ifndef __BMP_H__
+#define __BMP_H__
+
+#define BMP_FILE_HEADER_LEN 14        // BMP header length
+#define BMP_BITMAP_INFO_HEADER_LEN 40 // BITMAPINFOHEADER
+#define BMP_V4_INFO_HEADER_LEN 108    // BITMAPV4HEADER
+#define BMP_V5_INFO_HEADER_LEN 124    // BITMAPV5HEADER
+
+#define COMPRESSION_BI_RGB 0             // no compression
+#define COMPRESSION_BI_RLE8 1            // RLE8
+#define COMPRESSION_BI_RLE4 2            // RLE4
+#define COMPRESSION_BI_BITFIELDS 3       // Has RGB bit masks
+#define COMPRESSION_BI_BITFIELDS_ALPHA 6 // Has RGBA bit masks
+
+#define BMP_PALETTE_ITEM_SIZE 4 // 4 bytes per palette item (BGR + padding)
+
+#define BMP_RLE_EOL 0     // end of line
+#define BMP_RLE_EOF 1     // end of file
+#define BMP_RLE_MOVE_TO 2 // move to position
+
+// defined in bmpload.c
+VIPS_API
+int vips_bmpload_source(VipsSource *source, VipsImage **out, ...)
+    G_GNUC_NULL_TERMINATED;
+int vips_bmpload_source_go(VipsImgproxySource *source, VipsImage **out);
+
+#endif